There are quite a few gamers who have principles, and I question the ones that seem like they would interfere with enjoyment of the hobby. Refusing to preorder, or purchase day-one DLC or steer clear of games that offend you on some level are all fine, but when you blanket refuse to buy games from certain publishers because of dodgy consumer practices that don't seriously affect you, then it feels like sacrificing fun in the name of principles that maybe aren't that important.
For example, I see a lot of people who refuse to buy games published by EA, Ubisoft or Activision, then complain when they see a game by one of those companies that looks good to them. At that point, you have to wonder what the point of a boycott is, especially not when the game will likely sell with or without your important. The only thing you give up in exchange for those principles is the opportunity to play something fun.
It works the other way, too; I think it was Totalbiscuit who suggested that so many PC gamers blindly supporting Valve and refusing to buy any game that wasn't on Steam ran the risk of handing them too much power. In light of the increase in shovelware that's been put out on Steam over the past year, an issue which is only now starting to correct itself with the new storefront and curator system, we can see the risk of favouring one particular brand over all others based on principle.
I should probably clarify that this doesn't claim to represent all gamers. The other commenters in this thread have made it abundantly clear that gamers are not a collective and have no shared set of principles, which I think should go without saying, to be honest. These are just a few recurring things I've noticed that I consider questionable.