I can't believe I'm trotting out this cliche, but....even the best hitters fail 7 times out of 10. Yes, bunting is different than swinging away, but people talk about players "knowing how to bunt" like they expect, no, DEMAND that they lay down a successful bunt every single time they attempt to. They talk like since it's something they don't have to do very often they should be able to do it without fail every time they're called on to do it. If that's the case, then don't you expect a starting player to get on base every single time they called on to pinch hit? You get people talking like bunting is some kind of muscle memory activity, where if you practice it enough you can just do it in your sleep and always succeed at laying one down.