1) Many players never play the endgame content, and do not want to. To them, the "actual game" is levelling. I would say both modes are.
2) You could say the same about raiding: "Raiding is about throwing garbage in your way to make you play longer before you get to the actual loot." Reality is, the game is about progression. Being stronger than you once were. Paying to skip that is not only cheating the system, but also cheating yourself out of the sense of progression.