Sony Ericsson W810

So I generally have my phone on the vibrate and ring mode. This way I can feel it in my pocket if I'm in a loud room or on the bus and can't hear the ringer. However, when I plug in my phone to charge, the vibrate and ringer are still activated. Now why doesn't the vibrate turn off automatically when you plug it into charge?

My old SE automatically switched to a ring only mode when you connected the charger. Seems like this W810i should have the same capabilities. Am I missing something?
Thanks

(sorry for also posting a similar question on another thread but it's more appropriate as a new thread)