Points taken from: http://themovementfix.com/the-best-kept-secret-why-people-have-to-squat-differently/
"...There is absolutely no one size fits all squat position. If you don’t believe me, you are in for a treat. This article will help show you why athlete comfort should dictate squat width, why some people’s (not EVERYONE) feet point out (no matter how much “mobility” work they do), why some people have a really hard time squatting deep, and why some people are amazing at pistols while others can’t do them at all.
...When someone has difficulty squatting, or their feet turn out, or they like a wide stance, we all want to jump on the bandwagon and say “your hips are tight, you need to mobilize them”. If we say that without considering anatomical variations of the hip joint, we can be misled.
...Athlete’s won’t squat the same, and they SHOULDN’T!
...Athlete comfort will dictate the stance that puts their hip in a better bony position. There are narrow squatters and there are wide squatters. That may have nothing to do with tight muscles or “tight” joint capsules and have more to do with bony hip anatomy.
...Very few people are at the end range of their hip motion, so hip mobility drills are definitely a good idea.
...People will express their hip mobility in different planes, and that is not a bad thing."