In Illustrator, what's the key combo to get the little R in a circle up, for 'registered'.....?
Illustrator, and before that PageMaker specifically followed by Freehand Adobe and Aldus found solutions that "worked" in the reality of how things worked. There are several general solutions. First is that the font is sufficient. That practically didn't work at all in the beginning. And still doesn't work. Many font designers were most interested in Upper and Lower case A-Z and 1-0. Followed by a small set of symbols, periods question marks and such. But very incomplete. There was a very high desire for USERS to use these fonts because they were inexpensive and interesting. Complete well made fonts were simply very expensive.
A big part of this was solved by the development of the Symbol font which allowed the use of symbols in many different fonts where those symbols didn't exist. While the font was "wrong" and didn't necessarily matched the flavor of the basic font, it worked at all which was important.
Unicode was a bigger solution because it meant that fonts would be large enough to include glyphs for all kinds of things predictably.
And there are tons of other things, ligatures and swashes and characters that don't fit in their boxes correctly and change character depending on the characters next to them.
Time to allow better fonts to be created. Ton's of fonts have been created, and many designers getting paid for or otherwise motivated is difficult. Font availability and cost for experimentation and use has been very difficult. Fonts have very interesting attributes. The get reused all the time. The become identities for designers and companies. They live a very long time once created. It's not easy to do them well.
At the end of the day not every font having an ® character is merely an indicator to the rat's nest you expose when dealing with fonts. I lived through the development of a ton of this, in the eye of the storm, and it's definitely not easy. But it is fun.