Personally, I think it comes down to two things that are motivators for any given player: Pride and/or Determination, or a combination of those two. Pride can be of the vanity type, where a player wants to see his/her name in lights, or it can be the sort of pride where he/she is too proud to run. Same goes with determination... One can be determined to get better and better, not giving a hoot how many times they die, or what their score is. On the other hand, one can be determined to rise through the score ranks. There are probably a bunch of variables with how these two things mix for any given person. The value system is a funny thing.
This doesn't really give a specific answer, but the notion helps me to understand the question. This kind of question is pretty personal... I don't think you can look at a group of people and paint with a broad brush. So I can only answer for myself: I don't ever really plan on landing or living through a sortie. Partially it's because I'm fairly new and I suck still, and partially because I want to see what I can do. Most times in the MA, I'll only take 25% or 50% fuel, not planning to rtb. The only way to get better is to die hundreds of times and learn as much as I can, so that's the way I look at it. For me, it's fun to fight. Every time I merge, or get jumped, I learn something.
Sorry for not picking a letter.