number of people transported dictates how many elevator shafts are needed, and express elevators to the top mean less leaseable space on lower floors. so less people at the top means more leaseable space.
there is a lot of work going into optimizing elevators so that as few shafts can be built as possible while keeping wait times to a minimum.
Developers are in the business of renting out space, so anything that reduces rentable space is bad for business.
It's also why tall towers only get financed during times of easy credit; they don't make much financial sense otherwise. Most supertall buildings take many years to reach full occupancy, if they ever do at all; it is why the World Trade Center complex has not been fully completed to this date.
there is a lot of work going into optimizing elevators so that as few shafts can be built as possible while keeping wait times to a minimum.