Do You or Your Player Require Official Products?
For me, it's largely about trust between the GM and the players. And I can really only speak from the players' side of it, because I loathe being a GM (I'll do it if I really have to, but it's probably my least-favorite thing about RPGs...)
But if I'm playing with a GM that I trust...either because I've played with them before or even just because I feel like we're on the same general wavelength of what the game is supposed to be...then I'm fine with house rules and homebrew systems/settings. But I don't have faith that every GM makes house rules to make the game more enjoyable to play, because I've seen some that make rules that make the game easier for them to run at the expense of how enjoyable the player experience may be. I've seen homebrew settings that were a royal mess...and I've seen settings that adapted rules from completely different systems in order to make things run smoother.
If I trust the GM, I'm even comfortable with them choosing to handwave a lot of the rules. But for me, it's all about why they're doing it. I've had GMs say, "Unless and until someone starts blatantly abusing it, I'm going to skip encumbrance rules. If it's plausible for your character to be able to pack it around, I'll allow it...but if you start claiming to be packing four swords and two battle axes, I'm going to dig out the books." I'm one of those players who rarely gets any sense of enjoyment out of digging into the crunch of the rules...I'm there to help weave a story and if I have to spend half my gaming time on a calculator to keep up with the rules, that's cutting into my story-telling time. A lot of my favorite gaming experiences were situations where there weren't really rules that applied to the situation...so the GM just made something up, whether that was the GURPS game where all the PCs were wizards' familiars, or the smuggler our Star Wars group recruited had an AI wired into his ship, or our Shadowrun group had to try and shoot down an ICBM with some re-imagined P-38 Lightnings. There were no rules for any of those situations (or, at least, not rules that wouldn't have required hours of time to work through to apply them to the game)...the GM just decided on the fly how it was going to work. I wouldn't try that with every GM...I had the good fortune of having a whole stack of GMs in college who were great at either improvising rules for situations that were outside the scope of anything the game designers had included in the rulebooks, or reinterpreting rules when they were applied in non-standard circumstances.
All that said, if I like the GM and the GM decides that things are literally going to be run by the books, I'm fine with that, as well. Because I know the GM is not going to use the rules as a goad or bludgeon. If I don't know the GM...well, I'm more likely to trust them with official rules, but if the setting sounds intriguing, I'll give them a shot with whatever approach they're using.