What exactly is critical listening? Who does it?

I know it can always sound better with a better component, but the incremental improvement as this point is not something I want to invest the time or $$ in.

I use the term "intentional listening" when I make the effort to sit down at the end of the day and revisit specific albums in my collection or listen to new acquisitions / potential buys. My listening sessions might last 2-3 hours before I call it a night. My job during the day requires me to be analytical, and at the end of the day, I just want to relax and enjoy a well-recorded album or two. There is some aspect of critical listening to my intentional listening, but I'm not going deep into the recordings. I might enjoy listening for new aspects of particular albums or songs I hadn't paid attention to prior or whatever. Like others have said, listen in a way that you enjoy on the system you have put together. 

Critical listening is akin to critical thinking. Both terms made up by those who want to consider themselves superior in some way. Nonsense.