It's actually the lazy way. I only work once, then copy that work everywhere. The copying/syncing is surprisingly easy. If that's what you call "package management" then I guess doing "package management" saves a lot of work.

If I had to re-configure my devices to my liking every time I would waste time in repetition, not in an actual improvement. I configured it the way I liked it once already, so I want to be able to simply copy it over easily instead of re-writing it every time for different systems. It's the same reason why I've been reusing my entire /home partition for ages in my desktop, I preserve all my setup even after testing out multiple distros.

If someone does not customize their defaults much or does not mind re-configuring things all the time, I'm sure for them it would be ok to have different setup on each device.. but I prefer working only once and copying it.

And I didn't say that bash is the only config I have. Coincidentally, my config does include a config.fish I wrote ages ago (14 years ago apparently). I just don't use it because most devices don't have fish so it cannot replace POSIX/Bash.. as a result it naturally was left very barebones (probably outdated too) and it's not as well crafted/featureful as the POSIX/bash one which gets used much more.