I know it rains a lot in summer, but who thinks of going inside to do anything in Florida? That is the problem there. The Mariners had terrible attendance too when they played in the Dome, it had about as much character as a parking garage and that is the same thing I hear about the dome in Tampa.
Rumor has it after the A's, the Devil Rays are the likeliest candidate to move to Vegas. Now they might not sell 40,000 tickets a night in Vegas, but they will surely top the attendance they get down there in Tampa or in Oakland.