I view this to be the same as when the person at Outback brings my take-out order to the car. No tipping is expected in that situation.
If few people people tip room-service delivery person and the hotel pockets that service charge, then the union is asleep at the wheel.
Regarding pizza delivery, that delivery charge is to defray the recent increases in the reimbursement required for use of the drivers' personal vehicle. As it is covering his/her costs, I do not view it as having anything to do with the tip.