The concept is called Duty Cycle.

We have a 10W of power going through a load for 10% of the time for 1W apparent load over time

It's very easy to turn switches on and off but much harder to continuously vary parameters of a circuit. It can be done but requires more moving parts (sometimes literal moving parts)

Generally speaking it is better to have continuous (analog) control over the system as fast switching creates voltage &/or current spikes in devices which will deteriorate them over time. That being said, a lot of devices don't care about those things and we can change our rate of change during the switching to also minimize damages