How often are choices the 'selfish' one and the 'selfless' one? Even here. You save yourselves to not suffer physical pain or you save others so you don't suffer emotional pain and guilt?
I could put all the blame on you. You're the one choosing to die, I don't want to give up my life, all of it basically ends up as 'your fault' and I'm not in danger. I can say I'm 'respecting your wishes' so I feel better. But it'd be because I didn't want to feel bad or risk my life.
Or I can be the bad guy and save you because I don't want to give you up. Even if it's dangerous, at least my life is a gamble instead of yours being a guarantee. Not because of just the idea of 'saving you,' but because it's a bet on getting the outcome I'm happiest with.