Many people are significantly less technically savvy than you might expect. Every form really needs all of these conventions if you want to make your software as widely usable as possible (which is all consumer software at least, or should be).

So in fact I think it is the rule, not the exception.

Unfortunately you have to do a dumb JS dance to get these reasonable affordances. Hard to blame people for not reimplementing all this shit even if it’s critically useful for many folks.