Because it's not enough to pay them the equivalent of 3 brand new games EVERY YEAR for them to do that when you'll apparently pay that much ANYWAY.
I guess a large portion of MMO players are OK with the aforementioned style of leveling and at this point SE has to recoup some money so the direction they're taking is not surprising to me.
Games are big business now and corporations don't want to take big chances, understandable to a degree BUT there are plenty of creative/different ways to implement these systems that would please casual and hardcore players alike, they have to be polished and engaging but there is room for something new, there is so much potential.
The genre is so stale to me and I won't be handing my money over if it ends up being the same old thing..even with a Final Fantasy skin.
I will give it a chance no doubt, here's to hoping that Yoshi has some surprises in store for us.