Actually, it’s about Capitalism. Someone provides a service for money; that’s it nothing else. Wither Blizzard sells a boost, or some player sell’s it for in-game currency which they in turn sell for real life money. Once upon a time, people would make an account and sell leveled characters that way.
Me personally, wouldn’t buy a boost, or ask for a boost. I enjoy the leveling experience. It helps me learn the character, the class, the specialization. Nothing worse than getting to max level and not knowing what I am doing and being decremental to the group.
I believe it’s mostly a generational issue. The younger generation, the ME generation just want to optimize their time to only doing one thing: max level endgame content. There are also some in the older generation of players that have leveled so many characters over their lifetime they are just tired of the wheel.
One thing I will say about re-mix, the gear just having a main stat, maybe some stamina. I can then boost it with my prefer type of gems or tinker sockets. You would never need to try to design gear again around content, it would never need to be adjusted for content. We wouldn’t need to keep raising power levels of content ever new set of levels.