There's still a big (Ha!)  oversizing problem in men's casual clothing. Ever bought a tshirt from Old Navy and compared it to one from, say, Abercrombie in the same size? I don't care for either brand, but you will be swimming in the bargain brand shirt. The reason goes something like if you buy the cheap clothes then you don't care as much how you look, and people who don't care how they look are likely to be fatter. In this case the oversizing has more to do with averages than flattery, because guys are more likely to take XL as a compliment than a criticism.