Why do so many MLB players not sign autographs for fans?

Every Brewer game i go to, theres usually 1 or 2 people signing autographs. Thats it! Out of a 25 man roster for Milwaukee and 25 man roster for the away team. All these fans are the ones who go to support them and cheer them on and root for them. Even to run by and give everyone a high five. Especially bullpen pitchers or starting pitchers who aren't pitching that day.. What else do they have to do before games than come over and greet some fans? I don't understand why MLB players are like this, especially when all these fans want your autograph. Can somebody please answer this?