I feel like Larian is afraid to make a special or "chosen one" main character because of the trope that many RPGs fall in.
Their DOS2 is full-blown "chosen one", but instead of one chosen main character, you get an entire chosen party. Then you compete among your party to get one "really chosen one".
They actually are very popular, almost all playthroughs/guides you can watch are with origin characters. I have friends who never played with a custom character tbh. In their word, they felt boring.
The point of playthrough/guide videos is to provide guides and tips, as well as to show off your playthrough, to your audience. Of course they'd pick an origin character, who has a real connection to the world with a real story and all the extra dialog and interaction with the world. I'd do the same. I can show off 4 such characters to my audience with my playthrough, instead of just 3 plus my custom character's cool name. I don't think we can base on this to conclude that all the people who made those playthrough/guide videos
actually enjoy the origin characters.
Here's another thing. If I were to play this game with 3 other friends, and we know that the whole point of playing together is just to have some silly fun and mess things up, then I'd pick an origin character too, precisely because - again - the origin characters have a story with more interaction with the world, whereas my custom character is bland and doesn't really have anything that can be considered "fun" for a group playthrough. You could argue that "see, the origin characters have their purpose", but this would bring us back to something others have already pointed out: it's pizza v. a kick in the balls.