How many here live in areas with severe winters and rely on shore power to keep their batteries charged, heat their boats, or are tied to mooring balls in remote locations with cold winters? This is where such a system would make sense, especially if you had to leave the boat unattended for some reason.
A couple winters ago our town got seven feet of accumulated snow in two days and lost power for three days. The road to the marina was closed for three days due to fallen trees across the road and downed power lines. Thirteen boats sank. That's a lot of boats down in a town with a population of 9,000.
This winter we had two cold snaps of -15C (5F) with northerly outflow winds gusting to 50 knots that went on for weeks. If the power had gone out, more boats would have probably gone down.
Definitely not for everybody, but for outliers in areas with brutal winters it might make sense. That, and occasionally hearing a whisper quiet itty-bitty teeny diesel DC battery charger kick in automatically once in a while would be pretty cool