I have been wondering why too, and assumed it was basically the result of uncompetitive classing. Although my plan for this season is to race my Focus RS again (just a couple Tour/Camp events and a full local season), I've been thinking my longer term plan would be in an Evora or Elige. I certainly don't need any car I'm driving to be "the car" in any respective class, but I do basically want to be in a reasonably fair contest.
I also assumed, perhaps not fairly, the SCCA rules making machine generally feared classing any Lotus so it would dominate...so when faced with some performance uncertainty, lean toward a faster class assignment for any Lotus. I'm confident that was part of what went into excluding all Lotus vehicles from Street Mod when it was first created in the early 00s. Although, I have no recent knowledge of such classing decisions in the last 5-10 years.
"Fingers crossed" for competitive realignment regardless of how full of sh12 it am. ;-)
'14 Evora S
'13 Subaru BRZ
'11 BMW X5M
'06 BMW Z4M