Why not? Desktop CPUs and other components do it all the time. Why waste energy?
The actual overall energy usage while I’m using it is negligible compared to just about anything else. I would use more energy in the day running my stove.
If you can use your GPU at full power, why do I have to drink out of a paper straw?
A single commute to an office by car likely uses more energy than a lifetime of PC gaming.
Alternatively , a game/app might trigger boosts that can’t be sustained, or some instructions like AVX that are intensive that require dropping thermals to sustain.
Power state switching is very common and a very interesting space to dial in.