Ruin Explorer
Legend
IME GMs are much more heavily invested in the game. Most of my players don't go to forums or read RPG news or anything. They also purchase next to nothing and often don't read the rules enough. Thus, along with gaming with my kids, I have turned to simpler and/or OSR rules. I personally still love more crunchy systems, but that is mostly just reading.
I'd agree except for the bolded part - my experience differs quite a bit there - when the players are enjoying the game and actually understand the rules on a basic level, and the rules are accessible to them (i.e. online or in a portable, easy-to-read book), they often know them very well - sometimes better than me! Also, whilst some players never buy anything ever, quite a few others do buy player-oriented books, from what I've seen.