I guess that they have to monetize the game somehow. You can't keep servers running indefinitely, let alone pay for any additional content, based on one initial payment. As the subscription model is dead apart from for WoW and niche games like Eve, then this means paid for expansions and/or micro transactions. Having read the article about F2P in yesterday's Sunday papers, it could be a LOT worse. If content was all permanent, there would be less of an incentive for folk to log in regularly: I could take that month away from the game to play mass effect 3, skyrim, tomb raider or the next Dragon Age. That's a month I'm not spending in their store, and there's a chance that I might not come back if I did.
In future I think I'll adopt a more Zen like attitude. ANet aren't doing this because they're evil, or stupid, but because its their business model. I don't need, or have the capacity to play all the content and get all the achievements, and I'm kidding myself if I think otherwise. As much as the OCD in me likes completing all the content, if I'm honest it's far more fun to mess around in WvW, guild missions or fractals with you lot. A lot of the time my fun playing will coincide with new content, but I'm going to focus on enjoying some of it rather than grinding to do it all, failing, then whining about it.