Why can't "?" be used in variable or function names

Hey, I'm new here I'm sorry if I'm stepping on any rules.

Just have a dumb question, why can't the question mark character be used in JS as a variable or function name? I understand that there use for "?" as the ternary operator. However adding a question mark to a function or variable would add a lot of context and help to understand someone's code.

Anyway, thank you for reading!