Aaaaand since I just realized that my above post is wildly off-topic and doesn't have anything to do with gaming, I will try to make amends and actually post something relevant to the thread title:
Companies fuck up good rules systems because they make money selling rule books. Every player tends to buy the rules, whereas only the GM will typically buy support materials, scenarios, etc. If the rule books only change in very minor ways, like Call of Cthulhu did for six editions, you get people like me who quit buying them after the fifth edition because that's the only one I need. And I COULD easily have kept running the game with my original 2nd edition rules (the only other edition I own). I thought the CoC rules were fine as is and there was no reason for a 7th edition, but I don't depend on publishing games for a living and the folks at Chaosium do. I've played 7th edition and it's a downgrade IMO, but some people prefer it. And with their new 7th edition rules they now get to re-publish and re-sell nearly 40 years' worth of old, but now updated for 7th edition, splat books and scenarios.