You're making a lot of assumptions about people's stacks. Not everyone is running behind a third-party proxy. There are many reasons not to do so and many aren't up for debate (like regulation compliance). And that's ignoring the fact that most protocols aren't like HTTP and don't know a thing about hostnames, so the only way for a "gateway" to exists is using different ports - something that isn't always possible and may require a lot of work to adapt to.