One less thing to manage and think about, including cleaning up after myself. It may pull dependencies that I don't care about or want exposed e.g that would be picked up by some other thing. apt-get autoremove --purge or pacman -Rsc become a distant memory.

It's fire and forget and I can just focus on what I'm set to do.

Once I'm done with the one shot task, it disappears and could be garbage collected for all I care.

Some tools I did promote to being part of my user env but crossing that bar is a very deliberate thing, some are promoted to systemwide (root) and the bar for that is even higher.

It removes a ton of mental deadweight.