Yeah, because they are so much more difficult. Or more serious, while uprisings are a bit more difficult (not enough to call them "difficult enough" if you ask me, but that's subjective), not only are there much more flashpoints to run than uprisings, they also have a different design philosophy in mind, that might or might not be what you want to play.

They could just add a way to manually remove stacks from your character, this way everyone (not just every group, every single player) would be able to decide whether or not they want more of a challenge. There's player-activated scaling already in the game, at the training dummys, so should be possible to implement, e.g., an item that removes any stacks from your character for as long as you are in that phase/are logged in/whatever else makes sense. /sign for reverting mechanic nerfs