Well considering I'm a former gaming channel hater, I feel pretty equipped to answer this. Imagine you're a vlogger, you write scripts, you act, you think of subject matter, you use props, some of us write music and incorporate parodies, you entertain, you put on a show. Now you see channels getting far more views than you doing gaming, you think "Whoa there must be alot going on here! What is this all about??" And then you see someone start playing a video game, and go "Hey guys what's up today I'm playing such and such" and then they proceed to just tell you what they're doing in the game for about 15 minutes. It pisses you off.
You're like "I could play a freaking GAME WTF" And you don't understand the appeal. And you gotta admit, because of the over abundance of this genre, MOST of the gaming channels you come across are not doing anything original, and most are not entertaining to people who don't just want to see the game that's being played.
With that said, having been on this forum I've found gamers I have immense respect for. Those that go the extra mile, edit their videos to be entertaining, have quick wits and are very funny, do montages, think outside the box, and if more vloggers were aware of channels like that, they might not feel this way. On top of that, I've tried my hand at gaming a few times, and I can vouch for the fact that it IS harder than it looks.
However, being both a vlogger and someone who's done gaming, I'm sorry but it's not AS hard as sketches and vlogging and things of that nature. Some gamers will try to insist it is, I'm telling you it's not. It can be more frustrating, sometimes you have a great run of commentary going and then you lose the energy and mess up and have to do the whole thing again, but I'd hardly compare that to the amount of creativity that has to go into making a comedy sketch or an entertaining and funny vlog that makes points while being humorous at the same time.
But lets not also forget that some vloggers turn on a camera and just talk too. No matter what genre it is, there are those that put in the effort, those that don't, those that have natural talent, and those that don't. But over abundance of mediocrity, lack of understanding what truly goes into gaming, and the perception that no creativity is involved, are the main factors that cause the disrespect of gamers.