Why? You would show red after 1 hit, but what about after that? You can take hit after hit after hit, but after a part is red, no more indication of damage is possible. If that part (wing? Fuselage? Whatever) is hit after that point you're back where you are now.
There's no way to re-set the damage screen while in-flight. Not to mention you can ding your prop, rip your gear off, and any number of things to cause actual damage to your airframe, in which case you can't tell the difference.