Originally Posted by
Socronoss
I don't even think it's about the 3rd axis. It's more that you would have to design areas where you can fly much bigger than those where you can't fly. Bigger = more expensive. That's actually the only true reason for this no-flight discussion. A dev must have brought that up in one of their meetings: "Dudes, if we didn't allow flight, we wouldn't have to design these huge areas, small areas with as many obstacles (gorges, mountains, water bodies that force longer ways) would feel just as big."
Then of course these cost-savings convinced everyone else and there it was, the new-born "flying is evil" mantra.