I used i3 for a few years before switching to KDE 1 or 2 years ago. For me choosing a full Desktop Environment over just-a-window-manager is about getting all the basics already co-installed with it: a default file explorer, default calculator, default terminal other than xterm, especially a default network-manager GUI, a sys-tray already populated with volume / screen / power / bluetooth / mounted-devices / clipboard / clock & date, a launcher, a system-wide config GUI ... without a DE, every single one of these is a manual install (plus researching the best choices and verifying & comparing their quality live) and/or numerous configuration files in diverse places, googling their syntax / incantations ... since all this stuff is "side-show stuff" (ie not my code editor, browser, email client, office suite), I nowadays appreciate batteries-included when setting up a new machine, reducing overall time-to-code-editing. But the endless custom-tweaking back then was good fun back in its own right. =)

Excellent response, thank you. Ive finally understood the difference between "Desktop Environment" and "Windows Manager".

Calling this stuff "side-show" very much resonates with me. I set this stuff up once when I install i3wm on a new system, and it works well. The problem is when I want to do something that Id never foreseen, there I go into googling for the bash command I need, and that I find annoying.