But it does have dependencies (as any shell script tends to). e.g. it requires openssl for computing hmacs; and it needs either curl or wget for doing http requests.
Indeed. For a long time I was using my own fork of simp_le, but the code wasn't easy to split the file writing logic into per domain directories for certificates, etc.
Bash is GPL Licensed and does not ship with most UNIX-like systems. *BSDs don't ship it, macOS is stuck in the past, etc. As a BSD user myself, I install curl(1), but not bash(1) on my machines (or jails).
OpenSSL (an alias of LibreSSL when applicable - e.g. OpenBSD) is standard and available on virtually all systems.
Also, Why would someone prefer this over https://github.com/lukas2511/dehydrated ?