The same reason I use *nix on the desktop: I like to be able to poke around on everything.
It's really scary for someone new, but power users like environments where everything is modifiable and hate GUIs.
I like being able to configure nginx a certain way. I like being able to get into a psql shell and play around with my data. I don't want to just give someone a git repository and magically press some buttons in their UI and have it work, because when you inevitably realize you want to do something special, you're stuck.
Not to be at all rude or confrontational, but I think there's a lot of folks in the open-source communities that have no idea how drastically their numbers are DWARFED by the number of devs working in enterprise computing. And those enterprise devs often have no use at all for "poking around", for better or worse: their priorities are other, entirely.
Different strokes for different folks, but there's a lot more folks stroking the corporate way.
MS has been pushing more and more for all of their tools to be scriptable through powershell, to give you just that. Getting stuck is harder and harder these days. Hell, powershell has features I'd love unix shells to copy, like being able to import libraries and use their classes and functions like any other shell command.
