Look at it. Let's say you want to go to MK for the day.
First bus leaves at 7:45a and takes you to Epcot. So then you'll need to bus or monorail to TTC, then monorail or Ferry to MK. I'm guessing you'll get to MK no earlier than 9:30. It's OK, you can catch the bus back to the hotel at 11:30p from TTC. That's not absolutely terrible.
But, what if you want to go to HS? Hey, look, a direct bus there and back! Great! Leave the hotel at 10;25am, and be picked up at 4:30pm. Five 1/2 hours at the park? Not so good. Of course, you could leave HS later and make your way to Epcot to be picked up at 8:55 or 9:45, or TTC and be picked up at 11:30p. Not so good.
And if you want to go to AK? I wouldn't even want to try to guess the hoops you'd go through.
Many of these off site hotels use the "free shuttle" lure to get people to stay with them. But, it doesn't take long to realize any $$ savings (no rental car, no parking fees) just isn't worth it.