I'm not well-versed with their tornado climatology, however, my thinking on this is...
Typically, in order to get strong/violent tornadoes you need sufficient low-level instability and robust wind shear, both changing of wind speed with height and changing of direction with height). You also need the most intense ingredients to overlap. Of course having a discrete storm mode helps significantly too.
when you look at how these weather systems evolve which produce these outbreaks in the south, more times than not the system is beginning to evolve in the southern Plains so Louisiana tends to be on the "earlier side" of system generation and strengthening. given this, it is very difficult to maximize and juxtapose all the ingredients at their peak.
This could be totally wrong but that would be my guess.