OK, here's the thing about morning buses from parks to resorts:
Buses go out from the parks to nearby resorts to pick up guests going to other parks. Other than that, buses are only dispatched when there are guests waiting to go to a resort.
If you're trying to go from a park to a resort in the morning, it is important that you stand in the queue for the load zone for that resort. If you're sitting on a nearby bench or standing back behind the load zones, you may not be noticed, and a bus may not be sent.
At AK, the coordinator has a view of most of the resort load zones, and I know the a.m. coordinators do try to take care of waiting guests. At MK, they have a more limited view, but they sometimes have a cm standing in the load zones to act as their eyes. So you should have the best luck at AK or MK.
The Epcot coordinator has no view of the load zones, so they rely on bus drivers alerting them when someone is waiting. It can be hit or miss.
Studios may be the worst place to catch a bus to a resort in the morning, but they are in the process of changing how things work there, so it might improve.
All of this applies only to buses from parks to resorts in the morning. At about 11 a.m., the focus shifts from carrying guests from resorts to parks, to carrying guests in both directions, and from then on all buses are dispatched on a regular basis, whether there are guests waiting or not.