nofi's original question was about "not very original" basses generally based on Fenders. Talking about Alembics, Wals, or other boutique basses is fine but it has nothing to do with what he's asking.
The way I see it, Roger Sadowsky and others looked at the original Fender designs said "I can do better than that." And they've found buyers who agree. Nothing more to it than that. Most of these builders are not hand cutting bodies, they're putting together carefully selected components, some of them their own designs, and making products for people who want something that even a CS Fender can't offer them. Maybe it's the pickups, neck radius, preamp or any number of factors. May not appeal to you but it does appeal to some.
Nobody's "ripping off" Leo. These designs are not protectable, any patents on them expired decades ago and fortunately the USPTO rejected Fender's attempt to trademark the shapes.