I thought the Super Dome was never meant to be used as a shelter either (at least not built with that intention -- not sure that's what you meant). I seem to recall the owners agreed to allow it's use as such, but said they did not know whether it could withstand the expected storm.
The Super Dome was a designated "Shelter of Last Resort" in the State and City emergency plan filed with the federal government. Therefore, the feds made the unfortunate assumption that there would be adequate provisions. There was no mention in any plan of the convention center being used as any kind of shelter.
Check out the emergency plan the city filed in order to get their FEMA funds (that was obviously spent on other things over the years)