Hecarim's Saddle

Hecarim has a saddle on so why can't we ride him? His devastating charge could be that much more devastating. Or it could help us escape getting devastated. I mean if we can get inside a giant frog's mouth for a while, surely we can ride a centaur. I guess the hardest part would be making it look like the champ is actually riding on him rather than standing on top of him due to size/position and what not. But that utility would be worth it.