Huh? this is used because if you are below 10,000ft you don't care how much higher they are climbing, and if you are above 10,000ft you are playing in controlled airspace and will find out where you stand from ATC.
here we go again. King of the kids.
I use the same airspace as other pressurised aircraft and I want to know what level they are climbing to. "Flight levels" doesn't cut it. If i'm descending from 370 and some one is climbing to "flight levels" and G airspace starts/finishes at 180 then flight levels may require more transmissions with some cool sounding wally with fantastic airmanship.