You see, while some of the changes are merely revisions, many are also completely different rules. Despite what Paizo has said, there are conversion issues between 3.5 and Pathfinder RPG (your half-orc barbarian is going to be a fairly different character in PF-RPG). Many of the changes, some of them even good ones, are ones I would never have allowed in a "revision," but only in a new edition.
Allow me to clarify. If I were in charge of the world (or at least D&D), I'd make sure that in a revision, there were no actual rules changes that could retroactively alter a character or a campaign. Changing the price of magic item, clarifying an unclear rules, even adding a new piece of equipment or tweaking a spell is not going to significantly alter anyone's character or campaign. But if I'm running a 3.5 game (which I am) and was going to switch over completely to Pathfinder RPG (which I'm not), I'd have to deal with all kinds of changes to the game. Suddenly the most important spells in the game no longer cost XP. Suddenly dwarven armor is made of adamantite rather than mithral. Suddenly devas are called angels. Suddenly half-elves are the best diplomats in the game. And so on. You might see some or all of these things as good changes -- some of them are. But in my definition of a revision, they just shouldn't be part of these books. This is 4th Edition material. I shouldn't have to change my campaign just because Paizo needed cash.