Well, there are some of us who think rulebooks should be free.
The problem is that making most of your money from selling core rulebooks leads to splatbook proliferation, which in turn leads to very cynical customers who think, "I could make rules just as good as that". At which point they see through it all--because the RPG rulebook business is a massive game of Emperor's New Clothes.
You don't actually need someone else to write the rules for you. You can make them up. And most of us do, and have, and will again. (How many people house-ruled in a morale system for 3e? And come to that how come a game got released without morale rules in the first place? It's a complete mystery to me.)
You can spend the rest of your life playing a game based on one ruleset. And some of us do, and have, and will keep doing it. You don't need to drop several hundred dollars on the next version--you have to have a reason to do that.
So the real creative work--the value added that designers can really give their customers--lies in campaign worlds and adventures and fluff. I mean, you show me a long-term D&D player, and I'll show you someone who knows who Acererak is. Or Eclavdra, or King Snurre. Someone who remembers all those goblins shouting "Bree-Yark!"...
... so that should be the way games companies look for profit.