A dual display setup creates a natural split between things
Sometimes you notice things only when you don't have them. At work I have a dual display setup on my work desktop (arranged horizontally), but I only have a single display at home (mostly for space reasons). One of the differences I've noticed in how I use my screen space is that dual displays provide a natural division and split between things, because of the literal physical split between the two displays.
(I've been noticing this lately because I'm working from home, so for once I'm spending a lot of time doing the same sort of things at home that I normally do at work.)
This split tends to manifest in two ways, which I can call active and passive. The active type split is how I often wind up dynamically using windows as I work on something. On a dual display system, it's natural to open up a full 'screen' (really display) view of a Grafana dashboard on one display while using the second display to look into the specifics of what the dashboard is showing me, through terminal windows and other things. Similarly it feels natural to park documentation on one screen while actively working on the other, or use one display to monitor logs while I'm making a change on the other one. The passive type split is how I organize iconified or idle windows; rather than sprawl across both displays, they tend to wind up entirely on one or the other.
In theory I could split my display at home in the same way (it'd take some window manager support to make it convenient, but I use a very flexible window manager). In practice such a split would feel artificial. I'd be drawing an arbitrary line down my screen somewhere, with no particularly good reason for it except that I wanted it. The split in a dual display setup is anything but arbitrary, because there's a clear discontinuity and visual gap (one created by the bezels of the two displays). You can't have something straddle the gap and look normal.
I suspect that I'd still feel this way even if I had a single display at home that was the size of my dual displays at work. I would probably start splitting up the layout so that some things consistently went to the left, some to the right, and some in the center, and I definitely would have a 'maximize to one half (or one third) horizontally' option in my window manager (because a true full screen window would be far too big). But I suspect that things would wind up passively sprawled out all over, instead of grouped into areas. It would just be too tempting to expand things into some of that empty space with no obvious division between it and the occupied space.