It's the same story as with the guys... The girls are in search of sponsorship and support, and the industry will not support you in any way if you ride a 2 stroke in their weekly Mowercross or Foopercross TV commercial, sponsored in part by Monster Phleghm Energy Swill.
Ride a fooper and do good enough, and there'll be a paycheck in it for you....
Ride a 2 stroke and do good, or even WIN, and there'll be nothing for you other than fan support... Unless you want to accept one of Fonda's "Damage Control" fartbike rides like Cedric Soubeyras, in which they are basically paying you to ride a Fooper instead of giving their bikes a black eye on a two stroke 1/2 the size....
That's the ONLY reason why we have to watch this racing series which is a pale shadow of what it should be.