HTTP stands for HyperText Transfer Protocol. It's meant to transfer HyperText between two nodes over a network. If you're not transferring HyperText, then you might as well use another protocol or a mere String-based transfer mechanism.
Why do you think everybody uses HTTP for their APIs and server-to-server communication today but you rarely see HyperText in it?
I have a few theories, but I would love to hear more about HN perspective on it.