An old, unsolved problem: send to voice mail

Operators using corporate PBXs seem to be able to "send" a caller to voicemail, but they are about the only ones. When calling for someone, I would SO much prefer to leave a voice messsage for them, rather than try to dictate to spouse or child, and hoping it gets through. Likewise, when answering our home phone, I would greatly prefer to be able to bounce a caller into my kids' voicemail rather than try to take down details of the proposed outing to the local cinema.

Yet, AFAIK, this feature is pretty much unknown in homes. Perhaps many systems have some way to do it, but if so, the infrequency of use suggest there must be a learnability/useability bug with it. It needs to be very easy and very obvious to do.