Imagine that that you are playing, and at random moments, a 7 year old kid in the room blats out horrendous noise from a trumpet. It's probably really distracting. It probably puts you off your game, brings you out of the moment. That's what an ill-fitting ruleset, or one ill-designed for this purpose, can do to a player - be a horrible distraction.
Sure, but it might that that system doesn't work for that player. Another player may be able to work in that system without problems, and the player may be able to work in another system without problems. That's not to say that some systems aren't better-designed than others, just that there are personal preferences at play as well.