They are the admins of their devices, not you. And as admins they should have full control over the security policy, not you.
I can't agree with you there, a few years ago I installed Mint on my mum's old desktop. It was either that or pay for a new Windows license to "upgrade" to Win10. She doesn't have admin, doesn't even know what admin is and would be unwilling to learn if she did know.
Not all users need to be admins, in fact most don't want it.
Me, however, I get pissy if the machine stops me doing what I want to do.
Hybrid is best.
I use the GUI quite a lot.
But some things are just easier in CLI, especially if you have to do that thing often.
The other reason to use the command line is automation, it is very easy to write a bash script and run it as often as needed, if every day at midday you want to update something CLI is much easier.
e.g everyday at 2am, my rsync script runs to backup my important files.
e.g 2, I have a small script to combine all the pdf's in the current directory into a single file using pdftk. It is so much faster than any graphical way.