So that the average Joe does not start using DFS channels next to a weather station, but knowledgeable users can still use it when they are nowhere near one, like OP probably is and the vast majority of people as well?
This mechanism is pretty much useless and many times, as OP has found out, poorly implemented. Do you think that a 25mW EIRP signal from a WiFi home device will reach weather stations and military bases miles away? It can bearly cover a 50 feet radius area. And most people don't live near one anyway.