It sounds — and I don't mean to be rude — like you have not been involved in a "real" production environment.
Modern Unix environments are automatically managed with modular configuration systems such as Puppet or Chef. Sysadmins have little or no need to log into servers to configure them; they just hook the server into Puppet (for example), and Puppet will do everything required to mould the server into its correct state: Create users, install public keys, install packages, write config files etc.
Puppet in particular is so simple that you would want it even if you were managing a single box. Why? Because if that single box dies/is wiped/whatever, you just get a new box and point it at Puppet, and it will become identical (minus whatever data you lost) to the old one. Or need to buy more hardware? Just point the new box at the Puppet server, and you have two, or three, or ten identically configured boxes.
So yes, in a sense you're right; sysadmins won't waste their time creating a bunch of users, because they will let the configuration management system do it. :-)
You know... that's so blindingly obvious, that it had never even occurred to me. I'm in the middle of a home "IT refresh" right now and I'm trying to update the obscene amounts of documentation needed on how to configure every little thing.
Your comment just gave me a "the code is the documentation" kind of moment; realized I'd much rather have all that documentation checked into a Git repo somewhere as automateable configs. Thanks!