So as a layman, I'd say - thought it as a safety feature.

(with my camera, Sony), the battery in the camera
charged, just like on the laptop

With my little Canon is synonymous recharged the battery in your camcorder, but only if the camcorder is turned off. When I switch it on and extinguishes Ladekontrolleuchte. When I pull out the plug, he goes out as well.
On my notebook battery is always charged synonymous when it is switched on. When I pull out the power cord, nothing happens. I believe that with the notebook Manufacturer extra effort to drive for more security. Camcorder Battery will probably mainly through, as they save on these expenses.