That's also a bad reason to include it: to save lost perks.
The perks you pay for a 262, let's say, are gone. The perk price is established once you take off. The multiplier for perks is only applied to what you earn DURING that sortie. Not the price you paid.
Say the perk price is 200 (let's make it nice and round). Say the kills you earn net you 5 perks if you had landed. You lose the plane and bail, so that's -200 points already.
However you bail so you get half those 5 perks. You'll get 2.5 back. So you lose 197.5 perks instead of 200. The perk price isn't modified, just the perk reward is.
EDIT: something like that. I don't mean those numbers/ratios exactly. You get the idea.