> Because a high proportion of ISPs are obsessed with ensuring that HTTP becomes the only protocol that works reliably across the internet, by blocking any other protocol (often because of abuse). Yes, eventually that abuse will just migrate to protocols layered on HTTP, but welcome to the tragedy of the expediency of the short-term hack.
In the absence of a dedicated +1 button, I hereby award my +1 clueful commentary to paulj, for hitting the sad nail on the sad head. It's not just ISP's by the way; it's every clueless sysadmin in the world, which is a lot.
Additional +1 to the commentary below, which rephrases the problem as "multiplexing the Internet through port 80", which is another way of describing the same sad problem.
I believe the relevant debate/topic, which accurately and pointedly frames the problem, is the one called "net neutrality". It's a very important one. Maybe put in another way: The fight against tackling real problems at the wrong level. Seing as that is pretty much a human race condition, it's a tough one.