I suspect that the tours and signings are both a way of saying thank you to the fans for supporting him, and a way for him to just take a break. It's hard for anyone, Brandon included, to just write non-stop without taking a breather. He's already twice as fast as some authors I know, and that's not including the other smaller series he's writing.
Fans obviously want to be able to see Brandon, and as SoulcastJam said, they are a part of his energy. Without the fans, Brandon probably wouldn't have as much of an influence. Though, he likes to answer most questions with RAFO, so.
I am very excited for Oathbringer, but I'd like for Brandon to do his thing, because that's who he is.