because no one wants that. the overhead of those guarantees makes no sense given the diversity of protocols the "internet" is meant to create. people would just use faster protocols for their intended purposes. the beauty is that the degree of Net Neutrality that we do have was created with minimal regulation before 2015. Risking further regulatory capture now, given the issues with local isp monopolies, makes no sense.

So if ISPs are using deep packet inspection to figure out what you are doing to apply some prioritization to your traffic, then using a VPN is a way of hiding that from them. All they would see is a stream of random data flying by. The pessimist in me says they would probably start slowing all encrypted traffic and sell their own VPN service.