I've been surprisingly happy with Tortuga the last few times I caught it. The peanut butter, banana, and Nutella sandwich is simple but tasty.
As for the spring roll cart, I think the visibility of the cart when entering the land helps push sales. Many must see the line, walk over to see what's there, and then impulse purchase. It's also a good location for anyone waiting in the hub for a castle show, parade, whatever and that moving deeper into Adventureland would lose some sales. That said, I think they're popular enough that moving to a location selling other items risks increasing lines and people bawking that otherwise would purchase other stuff from the location.
Adding to your point though, they also lose sales when weather is poor and the cart needs to shut down. But anything they could build in the current location would require $$$ and maybe risks partially blocking Club 33 views.
