Not sure what cpus you're looking at but everything in the desktop space is over 4ghz nowadays. My last cpu was at 4.6ghz its entire life and my 3900x stays at over 4ghz on all 12 cores when doing a render.
Yes, I know, but it never actually goes below 4.0 for me on all cores when doing a render.
The 4.6 was referring to my 4770k which was at 4.6 on all cores all the time.