Not everyone wants to do research for every little purchase. XBox and PS controllers are likely to be at least good enough, if not the baseline of quality. A few weeks ago I got an XBox-compatible third party controller with Hall effect sticks, and while it's mostly alright, I found a weird issue where when I enter a specific mode in one game by holding the right trigger I have to have the stick centered or it doesn't register for about a second. This doesn't happen with MS's controller, and I have no idea how the input device can be causing something so specific.

Do people genuinely not know about 8bitdo though? It doesn't take a lot of research if you're in a store or recommended it by amazon

No, they don't. They're a niche manufacturer, of course they're not as well known as Xbox or Playstation.