I just can’t see any use I’d have for a tail. If it were long enough, it could help with balance, but it’d probably just get stepped on. Plus, all my pants would have to be altered. And it would make playing poker harder because it would wag if I had a good hand.
And I’ve never seen my dogs or cats use theirs for anything practical, either. My tail-less Manx cat had no disadvantages vis à vis his tailed housemates.
Bayliss doesn’t lament his taillessness as far as I can tail.
He did bite a cat tail once and quickly learned a lesson.
I thought about ordering him a funny tail for Halloween til I figured out how they are worn. Yeah, no…not doing that today. 
My rats do use their tails for functional purposes. They whip them around to keep their balance, similar to the way humans use outstretched arms when balancing. They also brace them against fixed objects when they’re reaching for something or standing on their hind legs. It would take substantial musculature for a human tail to serve such purposes though.
I was late to this thread; I only joined the tail.
Evolution and adaptation are amazing things. Squirrels are rodents, but the creatures we normally think of as rodents – rats and mice – have hairless tails. It’s fascinating that squirrels developed such lush furry tails. According to Google, they serve multiple purposes – balance and aerodynamics, a cozy blanket in winter cold, predator deterrence, and communication.
Sure, but what’s the poster’s thought, of the thought, of the thought of his name?
His ineffable, effable,
Effaneffible,
Deep and inscrutable singular Name?
(Aside: Nice one!)
At a minimum, women should get to grow one when we have a child. It would solve a lot of problems to have a nice long tail that could wrap around a little one and keep them safe while you deal with a boiling pot or carrying groceries.
I’m not suggesting that people would one day wake up and find they had grown tails. That’d be weird. I’m saying that I wish that people had never lost their tails.
I’m assuming that fashion designers would have kept up, and your pants would already come with a tail hole.
Although, women would surely get frustrated with the size variance between brands. Do I need a small? Or a medium? You never know! Do you think people would be self conscious about needing a big tail hole? Is it something you find at the big and tall store? Or maybe it’s like “girth” - guys are always exaggerating just how big their tail is!
Makes you wonder why dogs play poker. I’m starting to suspect that the painting isn’t true to life.
Wait…how are they worn?! My mind has gone to a dark place!
Tail workouts would be a thing! Big beefy guys on the internet lifting serous weight with just their tail! And there’d be a Dope thread all about the health benefits of doing regular tail lifts.
Hence my lament. We are missing out on so much!
A prehensile one would be useful.
Handy for those tricky soldering jobs where you have to get the iron, the solder and the workpieces together…
We’d have to deal with thieves, though.
“Be careful walking through those touristy places in Paris,” we’d have to warn, “The local who stops to talk with you may be picking your pocket with his tail while he explains to you how to get to the Louvre.”
I wish I had a long, long tail.
Someday I will. I hope.
And then I’ll show the kids in town
new ways to jump a rope!
. . .
BUT . . .
If I had a long, long tail,
I know that Big Bill Brown
would tie me in a tree!
He would!
Then how would I get down?
I don’t think that I would like it
with my tail tied in a tree.
The more I think about it . . . NO!
No long, long tail for me.
No, the painting is mostly accurate, except that very few dogs smoke pipes. Many English bulldogs, however, are partial to cigars, which they feel gives them a dignified Churchillian look. 
Somebody’s gonna have to redesign the Shitter!
As many times as I’d crack my tailbone on the hockey rink, something fluffy functioning as a pad would have been welcome.
You should read humorist H. Allen Smith’s The Age of the Tail (1956), which looks at the way civilization would change if people had prehensile tails.
https://www.ebay.com/itm/297704122307
Or you could watch these documentaries:
There’d be a movie trope about the slow sarcastic wag
Some people would insist they “prefer nubbins”. Others would insist that they have a fetish.
Tail transplants would surely be a thing. Consider being a tail donor they next time you renew your drivers license.
Do you think catching your own tail would be taboo (like masturbating), considered an athletic feat (like dunking a basketball), or something juvenile (like spinning in circles)?
Babies would surely chew their tail. Very nervous people might adopt the habit, too.
We’d have figures of speech like “I fell head over tail for her” and “stop wagging my tail” and “let’s high tail it out of here”
There’d be a Dope thread titled “If evolution was true, shouldn’t we have lost our tails by now?”
Interesting note about tails (says AI)