The other reason being that MCO is a major while TPA is not. And another reason, if you go to airnav and look up airports in Tampa's airspace, you'll see ARTCC being referenced to Miami, and airports in MCO's airsapce referencing Jacksonville. Swapping it around, back and forth, will be confusing for pilots. A majority have it down were they contact JAX CTR around 10000 or so after leaving TPA. Not too sure about the Orlando side contacting MIA, though.