It's not really all that simple. They can, and maybe do, designate pick up times from WDW to MCO, but Disney cannot control air traffic delays, on times, weather and staff scheduling. That leaves people coming in to MCO at random non-controllable times. You can't have people waiting for three hours hoping some other people will be coming in view shortly. Not sure how it works now, if someone knows, please let me know because I am curious. It will still have a steady reliable departure from MCO to work. Just throwing out numbers having a bus leave every hour immediately replace by another that will leave in 60 minutes. It isn't as crucial coming from WDW to MCO but some consistency has to be there to get it dependable and not ulcer inducing for Guests. Seems like I remember reading someplace that going from WDW to MCO has about a three hour window with most of that wait ending up at the airport.