I personally only use them to avoid unwanted pregnancies, but before you start lecturing me on STDs and stuff, allow me to explain...
So, as I've mentioned in other threads, although I fantasize a lot about the fertile aspects of sex, I don't want to have actual kids, at least not yet. Also I respect women a lot and I don't think it's fair for them to take all the responsibility in that matter. So, it's 100% their decision whether or not to take the pill or any other contraceptive method. Besides, I also think of the bleak future an unplanned/unwanted baby would have, and I'd rather not subject any innocent lives to that.
Still, like most guys on Earth, I really dislike having to wear those things. Maybe it's all psychological, but to me they do kill the best sensations, that is, if I get to cum at all. That said, I use condoms only when pregnancy is a real possibility. How can I be sure? Only by knowing the person well and if there's sufficient trust between us. And that's where the STDs part comes in. Of course I care about my own health, and being responsible implies caring about that of others too. So, in a nutshell my rule goes like this: either we know each other well enough and trust eacn other enough to have unprotected sex, or we don't have sex at all. Yes, I'm not all that promiscuous. And as you might guess, when it comes to MM sex, I have a strict bareback policy, but the same rule applies.
What about you, guys? Have you thought this subject through as much as I have?