It's coz of use cases. Consumer-wise, if you're gamer, CPU just needs to be at "not the bottleneck" level for majority of games as GPU does most of the work when you start increasing resolution and details.

And many pro-level tools (especially in media space) offload to GPU just because of so much higher raw compute power.

So, basically, for many users the gain in performance won't be as visible in their use cases