I think it's less about not trusting custom scripts than it is about ensuring that your unix muscle memory doesn't atrophy.
I spend a lot of time moving around different machines, processes, configuration files, logs, etc. And I stopped maybe 10 years ago to use anything that is not available on a base system.
I don’t use fancy shells, I don’t use aliases, I don’t write local shortcut scripts, etc.
I just use regular bash, combine base utilities in one liners, and live with it.
Maybe I loose 1s here and there when writing one liners compared to someone with a library of wrapper utilities. But that gives me an immense benefit: I am at home on any machine, any distribution, everywhere, without any configuration, with any user.
Sure, in a quest of productivity, I should also use Vagrant and Packer to create docker images with a development environment so that I can run Serverless troubleshooting containers on all my machines.
These scripts will surely help me triple the performance of my bash one liners.
I’ve heard Eclipse has good shell completion and support for oh-my-zsh too.
You start thinking about packaging.
I would be mad at any admin that would dare to deploy his helper shell scripts like “addup” and “count” on a machine other than his laptop.
And if you meant he could just have these things in his home, then it defeats the purpose of the original comment: trouble shooting and administering machines forces you to often switch user, machine, etc.
Then instead of having to remember how to check all these things, they just run "find_resource_hogs.sh" and voila. It also enables other people to troubleshoot without specific knowledge.
Of course you don't want to put anything in there just because it might save 10 seconds, but then https://xkcd.com/1205/
You are basically describing modern programming.
Script Language (or scripting) is a programming language.
And about the "real" programming language you can also trap yourself googling and installing yet another library (did you read the code?) and/or reimplementing existing tools from the unix programming environment.