With KDE you get a lot more than just a window manager. And i3/sway have a very specific usecase and target audience.

By the way I've heard some people combine i3 with KDE, using i3 instead of KWin (which is its window manager component)

Id never heard of Sway. From the page, am I right in understanding that i3 is for X11 and Sway is for Wayland?

	▲	OscarDC 3 days ago \| parent [-]
		Yes basically, it's not the same dev yet sway is heavily inspired by i3 and works with i3 config files. As you wrote i3 is x11-only and sway is wayland.