You need to consider where all of your guests are staying. If you're having a wedding at SBP and reception in that area and everyone is staying at one of the Epcot resorts you don't really need transportation. Or if WP / GF and everyone is staying at a monorail resort you wouldn't really need it. But if you have people staying at other resorts that would be relying on Disney transportation, you may want to consider getting a bus.
We will be providing it, because while it's not really a "fun" expense, it will add a lot to our guests comfort. I know how frustrated I get trying to get back to my resort at park closing. I would not want my guests, all dressed up, after our wedding to wait an hour or more to get back to their room. I feel like that would leave them with a bad impression while they probably don't really care if I have upgraded linens or bigger centerpieces, etc. Our wedding is also in August, so it will probably be really hot and could even rain, so I don't want them to have to walk from the ceremony to the reception even though it is not that far.