Saw speed change signs in the Peak District: they need to be across all of rural UK

The other day I was driving through the Peak District and going into any of the villages on the A roads I drove on, they all had had 30 mph in 400,200 yard signs (I have been searching for an image of them but can’t find them). Throughout the week driving in other rural areas of the country, why are those signs not anywhere else?

When driving in national limit areas and it’s a slow turn of a corner get to the end of it and your met with a village that’s 30mph and have a speed camera. If any heads up was given beforehand would be huge, rather than braking suddenly to not get points.

Are these signs only in the Peak District? Debating relocating because of how impressive those signs are.