Most indie releases, RPGs, Brawlers, Side Scrolling shooters, 2d platformers, shmups, metroidvanias, contra-likes, basically any classic/retro style game AND fighting games; they're all perfectly fine and enjoyable with an arcade stick.
"hardly anyone has them"... so? It's still supported and that is the entire point.
"most of them don't"...
I don't know where you're getting this from, most arcade sticks for console have been shipping with 8 face-buttons since the PS1/Saturn days. I personally haven't seen anyone with a 6-button arcade stick in the last twenty years, though I'm sure these people exist but they must be a miniscule part of the miniscule users.
Just taking a look on Amazon and doing a search for available arcade sticks... after looking through about 10-pages with like 22 listings per page, I've seen exactly three listed without 6-buttons:
1) some weird console called a pandora that isn't really an arcade stick but an actual full on arcade board that plays games, but I counted it since this list is short anyways.
2) a neogeo specific arcade stick
3) an atari arcade stick
Everything else is 8-button. If I search for Xbox or PS specific arcade sticks, they're all exclusively 8-button.
This is all besides the point though.
All of those old school arcade style games you mentioned aren't the bulk of game sales, you keep pointing to fringe things and acting as if that's mainstream. As far as "most of them don't" I was about the left and right sticks not triggers, every arcade stick I have seen only has ONE stick not two and you need two sticks to play the bulk of modern games., I never said anything about buttons, maybe I should have said L3 and R3 earlier to be more clear, when I said they only have one stick and then went on to mention L and R I was talking left and right sticks not triggers so there is clearly a misunderstanding here and that's my fault.