As others have said, a lot of times people "feel" how hard a hunt is and throw out 10 as a big number. That said, our average day is probably 7-10 miles. It's not as bad as it sounds though. Most of our hunts consist of a 2 miles in, 2 miles out loop. Do one of those in the morning and one in the evening, and you're at 8. We know the area we hunt extremely well, which helps out with knowing the most efficient ways to handle/keep elevation as well.
The more elk we run into, the less miles we put on. So it's a win-win.