Is it a case of one just being monstrously easier? Like how everyone makes an HTTP1.1 server but never a higher version.

HTTP1.1 was the standard for decades (1990-2015, technically still extant). People usually just "stop there" because it's what the majority of browsers and devices were targeted to support and does "just enough" of what they're seeking.

Of course you would make an HTTP/2 server, if you were looking for active push support and the like.

Also, HTTP/1 is amazingly simple compared to HTTP/2.

I can write you an HTTP/1 server in bash in an hour or two.

9293 takes 953 and incorporates the errata (20 of them) and 6 other RFCS, so in that sense it's easier since you don't have to check elsewhere for bugs or updates.

953 is 85 pages. 9293 is also 85 pages (with 13 pages of appendix), although they switched to a proportional font for the PDF so there's probably more text.

no, HTTP/1.1 was RFC 2068, then RFC 2616, now most recently RFC 7231. it's still the same protocol, but with updates and clarifications from over the years.