Why should the priority go to the call? You don't know if the person is watching a Youtube video showing how to give someone CPR, and the person is busy dying. Would you prioritise a call from a telemarketer over that? Tele-medicine is just one example. Who decides?

I completely agree with roc that once you start thinking about it, there are just too many holes in the argument for prioritising on type. "Type" can just be a synonym for "provider". There will be nothing to prevent carriers to push new protocols to a non-priority "type", if they don't pay up.

If voip calls get priority, what prevents me from writing a torrent protocol over voip? That would just be a waste of bandwidth. Prioritising will set off a never-ending arms race.