I am just commenting about what I've seen at concept artist desks / animation studios / etc.

Why is that?

I am not an artist and also dislike multiple monitors, though I will employ two of them on occasion.

My reasons are:

If the window and application management doesn't suck, one display is all one needs.

With cheap multiple displays and touch devices came an ongoing enshitification of app and window management. (And usually dumber focus rules)

Having to turn my head x times a day sucks.