It makes you play harder. The crowd can have as big an effect on the players it is cheering against. It gets frustrating. It's easier to get down when you're on the road. There are, of course, other factors than cheers and boos.
Travel is probably the biggest.
Guys are used to a routine, doing certain things at certain times. Class, practice, study table, dinner. Being on the road takes them out of that. That's a big part of it. You can get out of the groove on the road.