Many of the resort bus stops have a time board that lists the arrival time of the next bus to particular parks. They are pretty accurate. But, you have to leave your room in order to see them.
Disney could put the expected arrival times on
MDE, but that could open a whole can of worms. Bus arrivals and departures tend to be somewhat fluid....things can, and do, change. I can imagine the distress when guests saw an arrival time of, say, 5:45, for the bus to MK. So, the guest heads down to the bus stop. But the bus is just leaving. There is some variable. I guess that they could say the buses have to be there at the listed time...even if they arrive early.
I figure it's just better to just leave enough time to get where you're going.....and not cut it so closely that if a bus takes awhile to get to you that you are late for an ADR.