You say that like anyone actively playing WoW isn't buying the expansion at launch, anyway. So what's it matter? If you prepurchase you can get early access to features, so... great?
And pre-purchasing isn't the same as pre-ordering, just FYI. Pre-purchasing is paying upfront to own it before it's actually available, pre-ordering is just setting up an automatic purchase for when it goes on sale.
I'm just annoyed that they seemingly still don't have a reasonable method for people who want to purchase the CE to get access to the digital exclusive rewards before it goes on sale. I'd love to spend the next few months leveling my new allied race characters, since there's not much else left for me to do with Legion.