Mostly that "web development" translates to services built on http/s only. Web is capable of other protocols. But everybody's favourite runtime has become the browser.
“Web” is pretty tightly designed around HTTP as the central protocol and HTML as the central format and that's generally part of the meaning of the term as distinct from “internet” or “hypermedia” or “REST” (for a set of things that are each like “Web” but broader in one or more dimensions) more generally.
Semantics aside, there's a positive feedback loop between “chokepoints on the internet (corporate firewalls, etc.) tend to let HTTP/S through to where it needs to go but often not other things” and “almost everything gets done over HTTP/S”.
“Web” is pretty tightly designed around HTTP as the central protocol and HTML as the central format and that's generally part of the meaning of the term as distinct from “internet” or “hypermedia” or “REST” (for a set of things that are each like “Web” but broader in one or more dimensions) more generally.
Semantics aside, there's a positive feedback loop between “chokepoints on the internet (corporate firewalls, etc.) tend to let HTTP/S through to where it needs to go but often not other things” and “almost everything gets done over HTTP/S”.