A bit more intuitive Cycles CPU+GPU configuration

Currently user must go to system preferences and enable CPU as device for rendering under CUDA/OpenCL section. It is not too clear there for the user that this is choosing CPU+GPU for rendering at the same time, perhaps new user believes that there he is just enabling CPU as device for rendering.
Then from render tab the user must choose GPU, which is not very explanatory about what it may means CPU+GPU rendering .
If the user then wants to render only with GPU, again he must go to Preferences, System and disable CPU there.

Is this so for some technical reason or limitation?

I think it would be much simpler for the user if we could avoid CPU configuration from Preferences > System, and instead just add a section “CPU+GPU” under Device in Render tab. Another advantage of this would be that this configuration would be saved in the .blend file, instead of it depending on the configuration of each user have in system preferences.