Originally Posted by Maylander 
Isn't leaning fairly common in games with a cover system?
If it's a 3rd person cover system it doesn't need it anyway (field of view and camera panning remove the necessity for it).
If it's 1st person, it probably doesn't have it. Mostly because it was developed for console where they don't bother with it. Stealth games are usually the exception, but not always (DX:HR didn't have leaning in 1st person). Sometimes there is leaning on the PC, but not on the consoles (ex: CoD games).