>>15523263
While dedicated leaning buttons can avoid a lot of frustration due to non-recognized cover and such, they also are a lot clunkier in practice: they require two keys to be bound, ideally in an easy to access area, and they often need to be pressed twice in quick succession to peek out of cover.
Simply leaning out of cover while aiming is much more convenient and enjoyable in single player games, at least in my opinion.