You miss the point.
The point is that while the property owners can do what they like, the prospective *tenants* may have a very different outlook on the matter.
I doubt the property owners would want to build two more 110 story buildings only to have them remain mostly empty in perpetuity because the financial players have decided there's no good reason to all gather in one spot anymore (and good reasons *not* to).
People started crowding into Manhattan and other city centers before the invention of the telephone. The bandwidth revolution is making high-density urban areas more and more obsolete.