This.

Several of the top 10 deadliest in US history have occurred in MS. Many other tornadoes with lesser but still substantial numbers of casualties have plagued the state. Most of these are quite violent, earning F4 and F5 ratings. The intensity, coupled with the state's historically impoverished population living in cheap housing leads to disastrous consequences. Storm shelters or installing a basement are costly things as well. It's also my understanding that parts of the state have a high water table making it challenging to do anyways.