I also wondered about smells today actually. I ride icelandic horses on a regular basis (I own 2 horses myself, but I only train with one of them), and when riding these horses during the winter we use overalls. I have 2 but at best I wash them once every 3 months.
The riding gear for MotoGP-drivers seems to be made out of leather and the guys do sweat quite a lot... How often do those leathers get washed?
Wet leathers do not smell good at all, mix it with 6 months of old sweat and I would probably prefer to stay at least 10 meters away from it...