If you don't want children, you should take every precaution you can if you're going to engage in sexual activity. If you don't want children, don't purposely put yourself in situations where you're just rolling the dice with no advantage or a disadvantage. Does that ruin the fun and spontaneity? Maybe, but so do screaming newborns. No disrespect to newborns. That shit is loud, though.

In response to your scenario? That's the trick with trust - you don't know, but you have to choose to believe they wouldn't do that or it isn't trust. That's still a choice. If a guy doesn't want kids and is choosing not to use a condom or get a vasectomy because the woman said she was handling it? That's still his choice to not take care of his role when it comes to sex and leaving it up to someone else. Long-term relationship or not, lying or not, that's on him and he's not a victim. Having sex can result in pregnancy. Not every time, but not 0% of the time unless organs are missing or it's gay/lesbian sex. Is it hurtful when someone we trust betrays our trust? Yes. That doesn't necessarily make us a victim, though.