Because the features are a mix of A/C in that You have a C floor plan (for them most part, they're cheaper than the bigger class a's, and skimp on some of the normal A features.
From a marketing perspective I assume they are trying to compel those who want a class A diesel pusher look and layout at a Class C price.
No step down to the drivers pit. Overheard bunk (that I suspect most of us never use), automated leveling not typically found in B C class and a poor mans version of basement storage. Our FR3 bins are a far cry from a DP swing open full basement storage bin but for the $$$ I think many of us were willing to settle for these lower end diesel pusher style amenities to get into a lower price point. When I compare the layouts and bed space of the higher end line, I'm glad I chose what I did.