Looking over the GA Occurrence reports it is clear there are a lot on infringements, but it isn't clear how serious they are.
My feeling is that certain airfields have been 'encouraged' to report whereas once upon a time, they didn't
I guess it is a drive to create or extend Class D and avoid the hassle of a full-blown airspace change.
We've seen how quickly a TMZ or RMZ can be created compared to a change of Airspace Class. The SMZ is a natural and cheaper extension of this