Some people actually prefer loose-fitting clothes to tight ones.  Loose clothing has both practical and aesthetic advantages:
  1. More fabric means less chance of freezing your ass off if you live in someplace that has a six month winter.  Let's face it, tight clothing is intended to help you show off your assets, not keep warm.  Clothes that stave off cold tend to be very bulky or made of fabrics like wool that aren't the most comfortable to have against your skin.  Consequently tight clothes tend to be ill-suited to cold climates.

  2. Loose clothing operates on the principle of suggestion.  Since you can't quite tell what the wearer's body looks like, you're invited to wonder.  And wonder and wonder.  Perhaps if you're lucky there will be a gust of wind and you'll get to find out if you're right.  The anticipation is certainly more rewarding than the immediate ability to count someone else's moles.

  3. People feel more confident in loose clothing, since they aren't constantly on display.  They are likely to be more relaxed about their body and comfortable around other people.

  4. Come on, halter tops are nasty.  Artfully draped untucked button up shirts, by contrast, are good.  Loose clothing lets you look unkempt, which is very attractive.
Basically the choice is between instant and delayed gratification with regard to the human body.