Not only the bass buttons, there is a type of chromatic button accordion, popular in eastern europe.

https://www.youtube.com/watch?v=R2Z4iPyFmAE

And then there are diatonic accordions, which all use a similar layout both for the bass and melody sides (but you can't play in all keys[0] on them, that's the difference between chromatic and diatonic). While they are simpler than chromatic accordions, they are now usually more expensive because fewer people play them.

[0] that is, ~"scales"; usually all buttons will be working