Hussar
Legend
That's a point that I hadn't actually considered. I imagine that that might have some impact as well. Although, that being said, every single AL adventure is 3rd party. WotC doesn't actually make any AL adventures anymore, I don't think. But, on the player's side, you are absolutely right.I wonder how much of that thinking carries over from people who started (or are still in) AL or other organized play where only official first-party content is allowed?
Not sure how big of an impact it has though. The whole "if it's not WotC, it doesn't exist" is something that has been around since the very first days of the OGL. I think it has a lot to do with the fact that people go out of their way to buy WotC books. Whether it was back in the 3e and 4e days with the "book of the month" club, or even now in 5e where the release schedule is so slow that a given player can pretty easily own most of the WotC books. You go out of the way to buy the book - either through an FLGS or whatever - and you want to use that book. And you know, 99 times out of 100, that the DM will allow you to use stuff from a WotC book, no questions asked.
For a 3pp book, the player can't be sure that the DM will be groovy with using it, so, they don't buy it. And because they don't buy them, they don't bother looking at them.