The specific-plugs-for-lamps think is very rare these days. The reason for it is that it’s not uncommon for our plugs to be on a high amperage circuit - sometimes 30A, occasionally higher - that can’t be safely controlled with a light switch or similar, so the lamp-only circuit will be capped at, say, 3A with unusual plugs to avoid someone trying to connect a tumble dryer.
The specific-plugs-for-lamps think is very rare these days. The reason for it is that it’s not uncommon for our plugs to be on a high amperage circuit - sometimes 30A, occasionally higher - that can’t be safely controlled with a light switch or similar, so the lamp-only circuit will be capped at, say, 3A with unusual plugs to avoid someone trying to connect a tumble dryer.