I simply do not practice enough at extreme distances to feel like I can reliably take a 500 yard shot on game. I sight my rifles to give a point blank range (+-3 inches) of about 300 yards. At 400 yards I know I can hold at the top of the back on an elk and hit the vitals or just over the back on a mulie. At 500 yards three feet of drop is just more that I want to try on a live animal.
Besides, I have never had to shoot over 150 yards at any animal.

Where I hunt the terrain simply does not allow too many 400 or 500 yard shots. A few here and there but not many.
Also judging distances accurately in some of our terrain with out he use of electronics can be extremely deceiving.