I wouldn't call it blind loyalty.
I've used Steam almost since its inception, and by and large, it stays out of my way while playing, lets me install any game I've purchased historically without any trouble, and provides download speeds that approach my fiber's max limit when I do install a game. For me, it just works™. I've yet to have a bad experience with it.
Sure, I also use GoG semi-regularly, particularly because it's also been relatively painless to use but also because the often overlapping sales on both frequently result in games I'm interested showing up cheaper on one store than the other (but not always the same one). However, it started off pretty niche, and CD Projekt Red publishes their really big games to other stores (much to their credit), so I won't fault someone for not having used GoG yet.
I've also dipped my toes a little in the EA store, but only because there have been a few games I've wanted which required it. It struck me as an inferior experience to Steam and GoG, and I admit a particular distaste in the handful of cases where games bought on Steam/GoG still ultimately require launching the EA store before the games themselves load. If this is someone's first experience outside Steam, I totally understand retreating back to familiar territory.
I won't dispute if someone else claims having a bad experience with Steam - I just haven't shared it. However, I do find hate because "they want to make money" puzzling. Every store does.
I would say what you are describing is also not blind loyalty. But there are very much people who do have blind loyalty. I agree on not hating them just because they want to make money, but there are people that seem to act like Valve is their friend and somehow this saint for gaming as if they are a non-profit or something. I guarantee you they are not working on SteamOS out of the goodness of their hearts and it is more about their ability to retain control and fend off Microsoft more heavily pushing their store (yes I know you can run anything you want on SteamOS but that does not change that for most users the Steam store will be the easiest option for them).
We see a little bit of it on HN, but look at the comments on the Gist itself. This was also shared on /r/steam and the comments there. Or the fact that this is currently sitting at "flagged" on HN for no valid reason I can figure out.
There are a (seemingly) rather large subset of gamers that any talk of using another store is immediately scoffed at. Dare have to be critical of Valve/Steam (except for them not putting out games anymore, everyone seems to be in agreement that it sucks) and people try to pivot to all of the good things they have done as if that just makes whatever bad behavior they are doing justified.
Edit: Seriously, go look at some of the more recent comments on the gist attacking this guy and tell me there is not blind loyalty to Valve. Some of these responses are seriously unhinged.