They're useful to let you not have to think about positioning windows with precision.

If that doesn't feel useful to you, then maybe a tiling wm isn't right for you. That's entirely fine.

My wm has an "escape" in that I can define floating desktops, and by default I have one, mostly used for file management, because there are things where I agree it's better to have floating/overlapping windows.

It doesn't really matter if it's a "waste of space" - I have two large monitors, and 10 virtual desktops to spread windows between (I'd add more, but I haven't felt the need). To the point where my setup, by default, centers the window with large margins when I have just one window open on a screen because it's more comfortable (and I'm just one keypress away from fullscreening the app anyway).

Most of the time I use tiling because I like not having to care about the layout beyond those defaults.

But I can also configure specific layouts. E.g. I have desktop dedicated to my todo list, a list of done items, and notes, and it has a fixed layout that ensures those windows are always in the same placement, on the same desktop.

Maybe it's also due to differences in personality. I like to focus on one or two things at a time. And on second though, my argument about wasting space probably doesn't make sense. Perhaps I'm thinking more about "information overload".

In my day to day I have a couple terminals (each with 4-5 tabs, some are running screen sessions), two browsers (with max 3-4 tabs open), music player, at least 2-3 IDE's open (JetBrains), Notes, mail client, Slack. This is across two monitors.