Judging many of the categories is a highly involved process with the expectation that at least 4-5 hours are spent reading games and comparing nominees.
The ones that are public votes are explicitly popularity contests; the rest are not intended to be and the judging is taken seriously and we wouldn't want people who don't have informed opinions to vote.
That said judging is open to everyone. No one was turned down as judges. But there's an expectation that if you sign up to judge you're going to put in time and be objective as opposed to voting for your friends and that expectation isn't imposed on the public votes to the same degree.