>For example, I'd love it if my work VPN could be prioritized over someones pron torrent during internet rush hour.

That would be great for you of course by why should ISPs get to determine whose packets are more important especially if the entry criterion to being important is basically "pay up"? What if the reverse were true and other users' packets were prioritized over your work ones simply because Netflix, YouTube, Valve, etc. could afford it and your company decided not to?