You think remembering all function keys for every program is not a problem? Some remarks really amaze me.
You use function keys for repetitive tasks, if you don't repeat it enough to worry about, then it is a non-issue.
Discoverability for the common consumer is the problem this is solving, plain and simple.
The touch bar is instantly recognizable and serves as a status symbol, which is important for part of Apple's demographic. This is not sarcasm, just stating a fact.