They do. All the time. I can't tell you how many times I've had to log in to my learning plan to find yet ANOTHER safety-based training module.
They've beaten this dead horse so many times there's nothing left to beat. But no matter how much you plan and prepare, there is always a human element that is unpredictable. There is absolutely no way to completely eliminate risk.
Do I believe Disney is not to blame at all for this? No, there is certainly plenty of room for improvement. But WDW has a huge bus fleet with many drivers of varied ages and experience levels all expected to drive the same routes filled with, I'm sorry, but complete idiots (a.k.a. tourists) who freak out and pull dangerous driving stunts like pulling u turns, crossing lines at exit lanes, and driving over wet muddy grass medians, because they've missed their exit and frequently assume that's the ONLY EXIT in all of property.
I seriously hate driving to work every day because, honestly, half the guests driving here it seriously makes me wonder how they managed to get a license. Not to mention the fact that we haven't had MORE accidents up to this point. Let's face it, 99% of guests who drive here act like complete idiots on the road.