It's less about malicious intent and more about predictability.

When I install software on my computer with apt, I trust that all the files will go to the right place and install scripts are going to do sane things relative to the rest of the system. And I can just uninstall the whole thing with one command later if I so choose.

If I curlpipe a script, I get none of those guarantees. I have seen curlpipes that put files in weird places, guess the wrong OS, and mess with config files that I didn't want them to touch. When they break or I want to uninstall, I have to sit down and understand a (possibly minified) script to clean things up manually.

Yes containers are a half solution to this, no I don't want to use containers 100% of the time.

In countless corporate environments (including in highly regulated industries), far from being a firable offense, piping curl to bash is often a prescribed step in setting up the standard dev env. The cognitive dissonance is soul crushing. Maybe they're testing for one's ability to tolerate it.