Venom & V-Mach button pistons and compression cylinders in sliding breech rifles. Air Arms runs its springer pistons on circular plastic bearings, as does the Czech maker Slavia on some of its rifles, and the newish Walther LGV and LGU both sport rear piston bearings and make a big fuss about them.
As far as I know, if the buttons are made well from delrin or similar they do not wear down, they are super-slippery bearing on polished metal so there is very little friction. They can centre the piston and reduce vibration and make cocking the rifle super smooth (if that is important to you). The Feinwerkbau Sport rifle has very fine tolerances and doesn't need buttoning, but many rifles are improved by them if only to make the firing cycle slightly sweeter. I think also it depends on the interior finish of the rear of the cylinder, sometimes this is quite rough, and will need to be smoothed even if no buttons are fitted. Buttoning will also keep the piston central and stop the top rear edge from galling the rear of the cylinder.
It's up to you to not fit them, but if you don't you will never know will you ....