[lloeki]

Cordless trimmers are generally waterproof because some people use those under the shower.

Having them non operational when charging can very well be a safety measure so that they don't use it while plugged in.

There's really no excuse for headsets like Bose where such circuitry is a rounding error in the hefty price tag.

Hell, they even have USB circuitry that enumerates as an actual device on the bus but couldn't be arsed to have it be a proper audio class device.