Way back in the long ago days, they used to run buses to all the parks and hotels from the TTC.... but as the song says "That was yesterday, and yesterday's gone..."
Of course on one trip to WDW (our first trip in 1986 or 87 I think), they would run buses from all resorts to all parks, Downtown Disney and all the other resorts. They had this colored flag system where different color combinations indicated different routes... we were handed the little "key to the flag colors" when we checked into the resort. It was all very confusing.
I think it's much smoother now, but takes more time sometimes to get from point A to point B.