c.f. https://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html
User agents still don't support PUT et all in forms without JavaScript -- you're limited to GET/POST, c.f. https://developer.mozilla.org/en-US/docs/Web/HTML/Element/fo...
So why were they in the original HTTP spec if they weren't supported by original HTTP agents?
This is before me being old enough to follow technology, so below is a good portion of conjecture and hearsay (I'd love to be corrected by someone who actually remembers it):
Tim Berners-Lee initial web browser was intended as an editing tool as well as a viewer, and these ideas came back when they went to write up HTTP as a a "proper" IETF standard. Not uncommon (bit less so today, but back then especially) to design specs with what they thought it should do, not what they'd tried/done in practice. Making an official spec is the chance to get this stuff in.
At some point, a bunch of the file-specific stuff was split off to WebDAV as an extra thing (work on that started 1996, HTTP 1.1 was finished 1997) - or rejected and WebDAV created as a new home for those ideas? But PUT among some others survived.
Bad assumption.[1]
HTTP/1.0 spec (1996) defined GET, POST, and HEAD.[2]
HTTP/1.1 spec (1997) defined all of the other, newer methods.[3]
> supported by original HTTP agents
The first web browsers I know about were Mosaic (1993) and Netscape Navigator (1994) predating the HTTP/1.0 RFC.
[1] https://stackoverflow.com/questions/41411152/how-many-http-v...