I've wondered about this myself. I suspect it has something to do with guaranteed territories that protect the franchisee against a competing dealer within a certain distance. It's a common business practice. Under this logic, you could have a fishing dealer in close proximity to a non-fishing dealer because their product line is "different" so they're not technically competing. But each dealer becomes limited in what they can sell.
On the other hand, in the San Diego area, you've got competing Hobie dealers as close as a couple of miles to each other selling the same product. I'm sure there is an explanation which no doubt is complicated and at Hobie's discretion.
This is just one possible explanation -- don't know if it's on target or not.