That's the thing about rowing - you always have that option to quit. With 750m to go you are totally allowed to say "fuck this", get off the erg, and never look back but every rower I've ever met has something to prove, whether it's to their team, their coach, their parents, or themselves, they have to prove that they are stronger than they think. That's the thing about rowing. It proves that just because you have the opportunity to give up, doesn't mean you will.