What are buttholes for?

What gameplay purpose do the biomechanical buttholes serve in SOMA? Are they save points? Health rechargers?

Some of them need to be activated to progress the story but others appear to be optional; is there a bonus/negative to activating them all?

Solution 1:

They're used to recharge your health. If you fall enough to acquire a limp when you walk around, using one of the WAU sphincters will restore your legs.

As far as anyone knows right now, using all of them doesn't do anything. There are currently people trying to find speedrunning paths and techniques, so something might come out of that eventually.

It's rumored that there might be an alternate ending involved with these WAU sphincters, but the problem with that is the game forces you to fist the first one you encounter. It's possible that other than that first one, getting through the game without them could trigger something.