I think it's just capitalizing on a trend to add n't to otherwise noy contractions, to make them into contractions. Contractionn'ts, if you will

Yes... how is "reducing exclamation marks" a good thing when you do it by adding a ' (not to be confused with , ´,‘or’` ..which are all different characters).

Does this rely on the assumption that everyone uses a US QWERTY keyboard where ! happens to be slightly more inconvenient than typing '?

If someone really wanted to add it, probably the best would be to use unless