Why? Just because some people prefer to spend 10 minutes climbing to the thin air? I'd rather spend that time in a fight, and prefer to not have to climb over 12k or so...even then I'm usually 5k below everyone else and have to bait them to come down. So I like the low-alt base-take attempts and fighting amongst the trees and hills.
Besides, anyone can "fight" with 20,000' of air under them. It takes skill and control to fight when there's 5,000' or less under you, because you need to consider the ground and other obstacles as well as your foe - and maneuver your plane into a favorable firing position. 
In my case flying close to the ground or the water is a challenge because my frame rate is in the teens and I have all my graphics off so I can still play. The ground and water look like a drunken 4 years finger paintings to me. High fights are better but low down to the ground are way more fun. But this has nothing to do with this thread as is seems to have been hijacked lol.
