The integration is nice, it behaves as a normal buffer. So you can use all the standard modes and motions, splits, copy output to another buffer easier etc.

But modern terminals can do all that, with an editing mode that is tailored to terminal use rather than editing text.

Sorry I just don't understand why I'd want to use a text editor as my command line.

They can't though, a modern terminal cannot behave as a vim buffer. You can't have 25% of your terminal as a shell and the other 75% vim, they can't split like that. I'm not aware of any terminal that allows integration with vim registers or use vim motions.

You can use it as a normal buffer. Run command, switch to visual, go copy and paste. Way nicer than `:r !command`.