If I had to guess, I'd guess that less than 5% of current internet users have ever knowingly and intentionally used "the internet" via any protocol that wasn't

If I had to guess, I'd guess that less than 5% of current internet users have ever knowingly and intentionally used "the internet" via any protocol that wasn't HTTP. Even that might be an overestimation. Companies like Google and Facebook have effectively turned the web into "the internet" for the vast majority of people. Even e-mail has essentially become "the web" for most people thanks to services like gmail capturing so many uninformed and unsophisticated users. IRC, too, is mostly lost to services like Slack. Corporate interests have mostly erased the concept of an open, decentralized, multi-protocol internet from the public consciousness.