My theory: the Big Guy moved out of downtown because land and taxes are cheaper, many (most?) people enjoy seeing green as opposed to concrete, and the commute is often (not always) better, since most people live in the suburbs anyway. Couple that with an up-and-coming municipality willing to subsidize the building and infrastructure and you've got quite a lot of cash left in the budget. What do you do with it? Build an impressive structure, with the perks and eye-candy to lure the talent you're hoping to hire and retain.