The reason to rank up to 50 is not because of the current content, but for the content to come.

Everyone who says there is nothing different between 15-50 are wrong but not by much.. you have faction bosses and World Nms.

As everyone knows the game lacks content, but as for people getting to 50 at least for the majority of them, I feel very safe to say they are doing it to be ready for the Guaranteed Endgame events to come.

If you do not enjoy building a character or playing with friends to build a linkshell, then there is trully no reason to play at all atm, it is pretty much that simple.