It should be an option. Whenever your cellphone is charging, it means it is not in your pocket and is probably laying on the table. It would be a very nice thing if it wasn't doing this annoying noise and just play a chime instead.

I personally use Tasker and two of my profiles are to determine if I am at home or at work, based on the surrounding Wi-Fi networks. When I am at work, my phone goes automatically into vibration mode and when I am at home, my phone switch back into vibration+sound mode, just to make sure I don't miss my texts. However, I cannot change to sound only mode with Tasker. I am sure that Tasker users and many other users as well might be interested in that feature.