Of course, that depends on what level of playing we talk about. If it’s 3 or 4 chord songs using first position “cowboy chords” then yeah it’s easy.
But to really really play, it can get pretty involved, demanding, and busy.
Ok, now explain the Gibson Flying V (released 1958). 
Seriously, though. The shape of an acoustic was kind of dictated by tradition, and kind of by ergonomics. I wouldn’t really describe the first successful solid body guitar, the Telecaster, being “woman” shaped, even though it technically has a waist. It’s barely guitar shaped.
And really, if you carry this metaphor on through, it somehow means that you want to grab a woman by the neck and beat them on the belly while you sing. I don’t know what kind of weird stuff other folks are into, but that’s not what I want to do with the womenfolk…I would be so tender…and be so loving…you know it baby! <guitar solo>
Oh, and St. Vincent is indeed a god who walks among us.
A guitar is a lot more portable than a piano. Micing an acoustic piano can be a challenge. One can play lead or accompaniment on a guitar.
I read some incorrect stuff in the above comments that I MUST address. Sorry in advance.
When Les Paul demonstrated his solid body guitar proof of concept prototype to people at Gibson, they politely showed Les the door and when Les was out of earshot had a good laugh. They also had a good laugh when Leo Fender’s Broad/No/Telecaster began appearing on television. When their warehouse men complained of all the guitars in their warehouse and their sales of electric guitars fell off, they stopped laughing. When their salespeople reported that buyers preferred to wait 6-10 weeks for a back ordered Fender electric than to buy a Gibson right there on the shelf, they became worried.
So they got hold of a Fender electric, called in their luthiers and had a sneering session at it. Then they decided they’d use a traditional set in neck and a carved maple top on a mahogany body. And they’d use a nicer version of Fender’s single cut away. It was only AFTER several prototypes were built that Les Paul was contacted. Mostly because 1) they wanted to avert any law suit for stealing Les’s idea and 2) Gibson like to use popular guitarists to promote their guitars. Les saw the prototypes and had some criticisms and made some suggestions. Some they agreed to and some they didn’t. Les got free guitars and maybe $2.00 for each one sold.
But that’s true of all instruments, not just the guitar. It’s just that some of them, unlike the guitar or the piano, are difficult from the get-go (bowed strings, notably).
The first two points are true, but the one I bolded isn’t specific to the guitar. You can absolutely play lead or accompaniment on a piano. As a matter of fact, you can also play lead and accompaniment simultaneously on a piano (possible on guitar as well, but trickier).
Prior to the electric guitar, the expressive and loud solo instrument in the music that evolved into Rock n Roll was the saxophone. With a sax you could make the instrument sing and shout and emphasize passages by distorting and overpowering the notes. Then comes the electric guitar that can do all of the same things and ALSO let you sing while playing it.
True, picking a single string or strumming them is much easier than bowing. It’s later when you want to do more, that it gets tricky.
Playing lead (melody) and accompaniment (harmony, counterpoint) is tricky on a guitar. There are many places to play the same note, but depending on what other notes / chords are being played with that note, there may be only one spot on the neck where it’s possible. Then toss in the fingerpicking and string muting that may be necessary and it gets hairy.
The fingers on the fretting hand need to be independent of each other. The fingers on the picking hand need to be independent. Some notes have to ring and be sustained. Some need to be quashed. You have parallel and contrary motion. You have sweep picking and fast arpeggios. You have tremelo picking.
It gets more gnarly as you progress.
I’ve been playing since I was seven years old and there are still things I just can’t do.
If we’re talking about proto-rock, let’s talk about the first big stars. There was Elvis who was a singer. He played guitar, sure, but he mostly wore it as a prop. Little Richard and Jerry Lee Lewis played piano. Little Richard took a break to attend a seminary and Jerry Lee had that marrying a 13 year old cousin problem. Chuck Berry and Buddy Holly were guitarists. Chuck had some legal issue with an underage girl too but he didn’t marry her. Chuck brought Blues and guitar leads into rock. Buddy was a song writer too and compared to the others, was a clean cut musician.
I grew up learning wind instruments (mainly flute), I got free lessons at school because I was good at it and I wanted to learn. So I learned to play and to read music, which I still find kind of fascinating, the way that what looks to other people like blobs on a page immediately translates itself to music in my head.
I’ve always been envious of guitar players, I’ve loved the sound and the way that one instrument can convey so much in so many different ways. It’s an instrument I’ve always wanted to learn but never have. I’m also a massive fan of rock/metal music - I’ve been listening to it for decades, and (until covid struck) I was an avid fan of live performances.
Purely from a fan perspective, what attracts me to guitar-based bands is the energy and emotion that it brings, it makes me happy, brings me joy, and reminds me that life is worth living. Other acts (Elton John included) just leave me cold, most mainstream pop music is just background supermarket music to me, hip-hop and rap is just angry shouty people who found a drum machine and thought it meant they’d got talent, just give me pure unadulterated rock.
Probably my all-time favourite musicians is Danny Vaughn. I’ve seen him in various bands/collaborations, and as a solo artist, and an acoustic performer. Listening to him over the last year has been amazing, he’s taken so many songs from his band career and made them into acoustic versions that he’s performed from his living room via facebook (you can see them all on youtube). It says to me that a guitar is so much more versatile than other instruments, different types of guitar bring a different depth and quality of sound, something that really speaks to me on an emotional level. I can’t really find the words for it, but the sentiment is that guitar-based rock is a completely different animal to other forms of music, and it’s the one that grabs me and pulls me in, in a way that others simply can’t.
Just for starters a guitar may be strummed by a complete beginner for a musical effect where pianos can’t. It has a percussion aspect that anyone can do.
And further, an electric guitar can sound great sometimes just by accidentally touching it. Sometimes the notes and chords are not as important as the “Melange” It’s a very efficient way to harness electricity ergonomically and make it sound cool, no matter how inexperienced the player.
Footnote: I think it was Liszt who got those panties thrown at him way back when. The pianists were hot back then.
I think one factor that’s been left out is how well suited the guitar (especially acoustic, but to some degree electric) is for accompanying vocals. The range and timbre of a fingerpicked or strummed acoustic is just right to give a good background for a vocalist while not drowning or muddying the vocals – that’s not at all trivial (note that the most common sound problem with an electric guitar band is that the vocals disappear into the mix).
I don’t think it’s just accident or chance that as soon as microphones became good enough to pick up an acoustic guitar – this is before electric guitars and intentionally distorted sound-- the singer with a guitar became pretty standard.
After that, flexibility (ability to play lead with more or less the same instrument), ease of learning (at least the easy parts…) and cheapness all were important too of course.
I’m talking about before then. In the 40s, guitars were rarely used in bands because they were overwhelmed by other instruments.
Also guitars were far cheaper than most other instruments, at least for an entry-level instrument. Paul McCartney was given a horn that he exchanged for a guitar; in the Beatle’s biography, the author pointed out the music shop owner gladly took the exchange because the horn was more valuable.
Because it’s primary competition was the Banjo?
(Just kidding. But early on the banjo kicked the guitars behind in all genres of music. Volume basically)
You bette ask yourself why is rock music is (was) the primary genre played with electric guitars. There is no rock music without amplifier distortion. Chicken or egg?