Why do Jewish women/girls carry a suitcase on a day-to-day basis?

My intension in not to be rude at all, I'm just extremely curious. I've been taking NJ Transit for about 2 years now since I live around Teaneck, which is mostly occupied by Jews. I naturally began to realise patterns and clothing choice etc. One thing that always confused me is the suitcases, carried specifically by presumably school girls (?) What's in them that require such a big case? Does anyone know?

Edit: I come from Port Authority along with them so they have to be going to work/school in NYC.