I've actually found myself in the opposite situation. I just started wearing underwear again for the first time in years, and while it isn't nearly as comfortable as wearing nothing at all, I've never felt sexier or more aroused. I think it's about human nature and wanting a taste of what you don't have. If you were raised very liberally, I think that you will find societal restrictions, such as the "law" that you can only take off your underwear when you're showering, using the bathroom, or having sex, very attractive, while if you were raised very strictly, you will find rebelling and shedding your underwear very attractive. The grass is always greener...