I don't currently carry condoms but only because I'm in a committed long distance relationship, so I don't ever suddenly need condoms out of the blue. I also don't really appreciate one night stands and the like so I probably still wouldn't.
Yet if I weren't in relationship and I were out trolling for booty, I would carry condoms around. I think that if anyone is thinking of having sex with anyone soon they should always have condoms with them in case if the other person doesn't have any. Pregnancy and sexual diseases aren't as fun as sex, so it should be prevented if possible. I don't consider it "the guy's responsibility" because sex takes two people to do, and besides girls have to take charge of their own bodies. A lot of guys don't care enough to do so for them.