It was easier to justify hoppers, IMO, when Studios had nothing going for it except TOT and Epcot was THE place for a nice meal. Now that DHS has a lot more to do that's high interest and Disney Springs has obliterated the old dining rules of WDW and doesn't require admission I don't know that it's worth it to get them. I like having hoppers, but they're hardly necessary.
And it's definitely not like DLR where you can hop to the castle park and do things without it being an enormous hassle.
Personally, even if you stay on site I would take my own car everywhere except Magic Kingdom. MK is a pain if you drive. However, it's not at all difficult to park or get around to the other parks/activities with your own car and then you're in control of your own destiny.
There are a lot of people that don't like to drive on vacation and just want to take the buses, and if that's what they want, good for them. I'd rather not be beholden to buses or other transportation that may or may not arrive when I need them to, especially when it's so important to be there on time.