They're definitely not essential for every Linux user. I've been using i3 for over a decade now and I will not be parted from it because it lets me make tabs of terminals and then split windows with tabs of terminals and I can jump around between my tabs of tabs of terminals like a deranged monkey with all my fun hotkeys. I am not a well adjusted person. Most people don't want to spend the time customizing their window manager config to get it just so or learn a bunch of hotkeys. Most people like graphical file managers and graphical text editors. Most people should just use a regular ass DE.