Not to stay within more honest power limits? As now seems abandoned.
Engineers are just good at extracting more of the CPUs than they could before. More reliable circuits allow higher frequencies at the same voltage without failing. Turbo modes and advanced power management allow clocks that are generally higher because it can now be dependent on the load.
Imagine back in 1998 with the Pentium III 500MHz. It runs 500MHz when idle, it runs 500MHz when gaming, rendering, word processing.
Now if you want to spec the CPU for a power rating what do you do?
-Take the worst case scenario.
What if 9,999 out of 10,000 applications can run at 550MHz, while all 10,000 applications can run at 500MHz?
-You sell it at 500MHz.
What if 525MHz allows operation flawlessly for 5 years, but runs into problems later, and 500MHz can run nearly indefinitely.
-You sell it at 500MHz.
1 bad news counteracts hundreds of good news(and goodwill) thus as a business you try to be conservative as you can.
The Power Control Unit allows precise control of power used, so it does not deviate from what the company wants. Turbo mode allows setting different frequencies for different scenarios.
What does not change is fundamental limits. 5GHz is roughly such limit, since
5.5GHz on water has been true for 15 years. That means 5GHz CPU has no overclocking headroom.