This may have been covered before, but I was watching an old show on my “set”. Seems it was common years ago to use that terminology. As I understand the word, set infers a group of objects, but a tv is one thing. Why was it referred to as a “set”?
A set of tubes, in the original configuration, before solid state and transistors.
Part of the answer may lie in the fact that the English language word with the most definitions (at least according to Which Word Has The Most Definitions? ) is the word “set.”
That’s why I refer to my FiOS box as “the Internet set.”
Just a WAG: It may harken back to the days when TVs and such were more furniture than appliance, and TVs often came in a fancy wood cabinet that also included a radio. My grandparents had one of those, dating from the 1950s. Big honkin’ unit. So a TV “set” was the television, the radio, and the bigass cabinet that enclosed both. Eventually things got smaller when transistors came along, and the two pieces of electronics were separated. But people were used to saying “TV set”, and it just stuck.
“Radio set” was the commonly used term for a home radio at the time home television appeared. My theory is that the term “radio set” comes from what my people called a radiogram, a single unit combining a radio and record player.
Well, you’re all getting closer. 
“Radio set” was the term used for wireless radio sets around 1912. This certainly rules out any later tv origination.
Tubes–nope.
I have no doubt that whitetho might come along and tell us. He’s the guru on early radio.
And here’s a 1912 radio, a “set” of various components for receiving radio waves.
Radio receivers became know as radio sets, and I assume that this usage was simply passed on to TV receivers when they were developed, which inside the cabinet were a collection of tubes and other components.
My family had one of those in the 1950s, which also contained a record player. But the whole unit wasn’t the set: the unit included a TV set, a radio set, and a record player. Later when we got a separate TV we also called that the “TV set.”
Now I understand. Television is a series of tubes!
Which is now in the process of being replaced by the intertubes… 
“Set” (noun, verb, and adjective) occupies 27 pages (p. 523-550 in the Si-St volume) in the original OED and is the longest entry.
I certainly recall “radio set” used before TV became a consumer item (around 1947) and then “TV set” was a natural extension of that usage. I had assumed it referred to the set of tubes, but it apparently refers to the set of things used in the entire apparatus. Nowadays, I just refer to “the TV”.
I think “set” in this case is a sorta-shorthand for “set up”. In other words, a coordinated collection of components arranged in a particular way.
Younger folks may have a hard time with this, but in the early 20th century, very few machines were “no user servicabe parts inside”. And very few machines were “intuitive”. No matter what it was, from a wringer washing machine to a tractor to a radio, it required a bunch of user understanding to operate and user maintenance was expected.
As a result, users understood their devices at least at the high level we’d call a “block diagram” today and would know the names & functions of the major parts, as well as how they worked together to achieve the result.
Consumer broadcast radio receivers were probably one of the first consumer devices whose innards were pretty mysterious to their owners. But they became popular years after hobbyist & professional radio folks had established “radio set” as the standard name.
a type of early radio device use was to make things modular. the components were separately placed on small wood boards and the components could be changed when desired; like a different tuner in a crystal receiver. this was for home or experimental use, both receivers (crystal and tube) and transmitters.
a collection of things to perform a function is a set.
the word may also have come from ‘setup’ early radio used for two way communication where huge room sized things.
other related
often a hobbyist would use a flat wood board (a breadboard) and mount components and wiring connection points on nails. later when other construction methods where used (metal chassis, soldering) this method would still be used for prototyping. breadboarding is a term now for developing a prototype.
if a radio receiver and phonograph (later tv) were together, they where called a console referring to its being a piece of furniture. even if it was a single device as long as it was freestanding on the floor it was a console radio, console tv. this for USA.
I’ve just researched and done an article on this. In the early days, “Television” 9a term introduced in 1900) referred to the entire process of sending images across wires. The device responsible had a different name, one of which was “telephote”. One used a telephote for television as one used a camera for photography.
The term telephote (first used in reference to a device of Alexander geaham Bell’s, and popularized by Jules Verne and Hugo Gernsback), however, fell out of favor. Although you could still find it used as late as 1935 in electronics dictionaries and the like, the term was dropped probably in response to a French camera lens, the Telephote, an early Telephoto lens. Perhaps to avoid confusion, people talked about using “television apparatus” or “television set”, as if the term “camera” was suddenly avoided, and people took to calling it a “photography apparatus” or “photograhy set”.
Eventually the “set” part was dropped when referring to the receiving device, which was called the “television”. But “television set” lived on as a sort of “proper name” for the device. Although, clearly, people had pretty much forgotten why.
IMO, a television set consists of several components put into the same body. All of these components are available separately, but are bundled together for convenience. There is a tuner, a monitor, an amplifier and at least one speaker.
BUT - the bundled package is what I would call a modern TV set. Back in the early days of television, I doubt that you could buy all of these components separately at the consumer level. I don’t know why they were called sets 30 years ago.