The continued drying of the American south west has led to stronger EMLs which have ruined the more conditional days that used to produce widely scattered supercells. In the past those conditional days produced some of the more photogenic tornadoes, and we just do not get as many of those days now. Additionally, several the bigger set ups have been ruined by excess moisture, which I think is probably tied to a warming gulf (and oceans in general). I don’t really see anything that makes me think either of those issues are going to improve in the near term, in fact, I think it’s more more likely that they get worse.