The explanations and reasons are given above but it comes down to the fact that domestic radio sets are not manufactured to a high standard and are susceptible to "breakthrough" from stations they are not tuned to for a variety of reasons. I am a radio amateur and, for our sins, we become involved with neighbours having problems with breakthrough from our transmitters. As well as radios, one neighbour of mine used to hear me on his hi-fi record player. When I asked if his hi-fi was designed to receive radio transmissions he got the gist.