Purely 'Try before you buy' for me but some games only got foreign, (US/JAP) releases so those I play without paying. (Tales of Innocence English translation for example).
I also like to collect. I buy a game than dump the ROM myself and play the backup so I can keep the original boxed and in good condition. I still a lot of have PS1 games that have been used once, to rip them, (FFVII and FFVIII, both with case and instructions, worth a bit already).
I think I'm legally entitled to do that though, aren't I? What exactly is the law on playing backups of stuff you own?
EDIT: Grrr, typos.