The birders and wildlife photographers get higher pixel density and framerates with an APS-C body, and save unnecessary space on memory cards and hard drives as compared to a full frame sensor, and all else being equal, the body will be considerably cheaper. Essentially the same reason that there was both the 5Ds and the 7DII. The cost-aware buyers have a path for starting into RF-Mount ILCs with a cheap APS-C body and adapted EF-S glass, but over the course of time can buy one or the other RF lens and later upgrade their body to full frame. The slow, low pixel density and not very rugged RP requiring expensive RF mount full frame lenses from the start does not cater to both of these groups....but you're not buying a full frame camera. You're buying an APS-C sensor camera. Just one with an RF mount, engineered for full frame glass. Unless we're getting some RF-S lenses, I just don't see how it works - am I being dense? what am I missing?