On Windows/Linux, I use a 101 key. We all know the symbols. And those are the ones I use. There are cases in which I can use an interrobang or kanji-related emoticons, but I'm doing a google search and copying and pasting. But long story short, I don't use these other symbols because they're not easily available.
Sure, I could remap my keys, at least on Xorg. (No clue how to do that on Windows. ) But then, those symbols just aren't used. It's also a reason I don't bother with APL, because the language uses dozens of characters that aren't normally on a keyboard. I'll mess with ones I can type.
Now, phones... Oh my. A phone will auto-substitute picture emoticons from things like :D . Technically, these are a Unicode character set with device implementations. It means even though the pic is a 32x32, it's only usually 2 bytes (unicode is fucky, urgh, so many bugs). I'm more leery in using unicode because of character handling and badness, but things seem to be moving that general direction.
But for the wider issue of Unicode, these "failed symbols" are right in there. But good luck exploring and finding them, since characters can be from 1-6 bytes, or 2^48 space... Alas, back to searching google and copying and pasting.