It takes up precious mind space for an ad-hoc one-off feature, instead of utilizing simple well-established unix commands commonly available on servers and usable for multiple purposes. Plus I'd say it gives a false sense of security because a moderately determined attacker can easily obfuscate his exploit so as to slip through this casual review process.
The mind space argument breaks down because its generally an install process which means you are just typing what they wrote in their README.md file if it seems reasonable. Its not something you memorize.
I think the "mind space" is knowing how to handle data, run an editor, and chmod or run a shell with inputs (all useful, portable skills), versus having a limited-use hand-holding script.
