The thing is - the polish matters. You can't do viable consumer apps until they actually work like the consumer wants, which is often decades after the technology preview. You could emulate websockets using IFRAMES, script tags, and long-polling back in the late 90s, but a.) you'd get cut off with the slightest network glitch and b.) you'd spend so much time setting up your transport layer that you go bankrupt before writing the app.