Afaik it is a safety thing that is handled differently in different countries.
Uk and their colonised countries have this. The reason is that the fuses are in each plug. But no (or almost no) fuses in the power grid of the house. In Europe most countries have a single GFCI and several fuses for power grid sectors in a single place in the house where the power comes in.
I assume the switches on the power outlets are for turning off a switch because there is no GFCI in the house.
Well I would need to do research on that so I can make actual claims here, but I think the switches on the power outlets are somewhat related to the kind of how fuses are handled.