There some efficiency gained by relocating a lot of the desk clerks to MCO from each of the individual resorts. Basically there are times at each resort where the clerk is not helping anyone while another resort has a line of guest waiting to check in.
Disney can "fix" the baggage issue by offering free check luggage if you book using your "Disney Rewards Visa". But those of us that fly Southwest, don't have to pay to check 2 bags.
There is also efficiency gained by reducing the number of trips by the trucks transporting the luggage, since everyone would be in the parks, the drop off time could be guaranteed in your room by 8pm.
The buses could still pick up / drop off at each resort but those buses would be servicing more resorts per trip and take longer.
Wait..... the real profit is in the souvenirs sales. It is odd that the drop off spot is not at DTD for purely profit reasons.