And a lot of what Ritter Sport wrote in post #36 are the underlying reasons.
" I can think of sentences that end in “should’ve”"
Should’ve is a contraction that I have never seen before. I can’t think of any good reason for anyone to use it either.
Quoth the raven, `Nevermore.’
Unless you’re talking 'bout Midge You’re.
And you forget how to spell his last name.
“Shoulda, woulda, coulda.”
But that’s rather informal, slurring the “'ve” contraction ending.
Unless it’s in quotes, you should never end a sentence in “you’re.”
In July the artificial kidney was finally put; no longer would she be shackled to that monstrous machine.
I had a dirtier version but I decided against it.
We need to have all widget pre-assembly lines ready to go by July. ***In ***July, we will flood the whole damn world with widgets.
Rookie mistake - Those assembly lines need to be ready to go by May at the latest:)
Well, you should of.
Perhaps my pronunciation guide wasn’t quite accurate, unless you say it really fast.
Think of it as “goin’-a the store.” Like in, oh, “goin’ a-hunting.”
I’m just glad I’m not as much of a gambler as Orson Welles.
Yes, anyone who has does so should not have had or, in the interest of time saving, shouldn’t’ve’d.
Contractions represent how words are spoken, in cases where we naturally elide sounds. No one naturally uses “you’re” at the end of a sentence. Technically grammatically incorrect? I don’t know for sure, but it simply isn’t done. 
Not the same thing. We go to the store. We don’t go to hunting.
I don’t know enough about grammar to formalise it, but to my mind it’s something to do with the fact that most of these formulations with the contraction at the end of the sentence sound off because they contract an important word that ‘needs’ to be stated in full, whereas using “you’re” or “you’ll” in the middle of the sentence puts the stress on “you” - the modal verb is less important.
I’m gonna the library later, so I’m gonna look it up then.
I think this rule about contractions at the end of sentences is as just much a strict matter of grammar as whether one should say, “I’m going home” rather than “me is going home.” Yes, someone could probably figure out that “me is going home” is the way that someone who isn’t a native speaker of English is trying and failing to say, “I’m going home.” Similarly, someone could probably figure out that “I’m a faster runner than you’re” is the way that someone who isn’t a native speaker of English is trying and failing to say, “I’m a faster runner than you are.” Grammar isn’t just about meaning and the choice of words and grammatical items. It’s also about the proper use of variant pronunciations of words and phrases. As I said before, this rule is mentioned in standard grammar reference books for English.