While gaming is one reason I need as fast CPU, it is not the only one. Besides building, testing and benchmarking new things is part of the fun for me. Also as I'm passing my current setup to someone who needs it, I have to buy basically everything anyway, and just don't find myself too interested in investing to DDR4 motherboards or sticks anymore. If I only needed a new CPU, it might be different, but I need a new CPU, GPU, PSU and memory anyway.
EDIT: if 5950X was reasonably priced, it could be an option, but it cost 700€ here! Same as 7900X only a bit less than 13900K.