Exactly, there is a reason (or at least there used to be a reason) why it is called WDW RESORT, not WDW theme parks.
For somone that goes specificaly for the parks, or that only goes ever few years, I can see them skipping Splitsville. But for local or "regulars" it is just another thing to do.
Golf - depends where you;re from and what you normally play (quality of course wise)
Mini-Golf
Water Parks - people may not have these local
Race Car Driving - highly unlikely people can find a local track that allows a lesson and rental of a nascar/exotic car
Fishing Excursions
Watersports - again, not everyone can just go wakeboarding / parasailing
Shopping
Dining
Concerts - again, if you aren't from a major city good luck seeing quality known talent
Shows (La Nuba) - see above
Boat Rentals - something people also don't normally go out and rent a boat
Trail Rides
Off road Segway tours - see pretty much all above
and now
Bowling - but the concept of upscale bowling isn't unique, whereas the options highlighted above are definitely somethings you ONLY do on vacation.
All things other than theme parks that people can do. Do a search on these forums and you will find a number of threads where people ask "have you ever gone to WDW and not gone to the parks at all?"
-dave