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

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.