Intel CPUs will rarely run at the base frequency unless you disable Intel Turbo Boost and literally force them to run at this reduced speed.
The Windows power plan controls what speed Intel CPUs run at when in Windows. If you are using the Window High Performance power plan, your Intel CPU will use as much turbo boost as possible all of the time, even when lightly loaded.
If you want your CPU to slow down when it is lightly loaded, use the Windows Balanced power plan. If the C states are enabled in the BIOS, there is not much reason to slow down a modern Intel CPU. They conserve power when individual cores enter the low power C7 state. In this state the cores are disconnected from the internal clock and they are disconnected from the voltage rail so they will be sitting dormant at 0 MHz and 0 volts. Most people still love to see a low MHz number when idle but this is not necessary, especially on a desktop computer that is plugged in.
Here is an example of a 10 core Intel CPU running very efficiently at 5000 MHz. Most people automatically assume that power consumption would be a lot higher. It is not when the C states are enabled.