Try it. Move your Steam window around. See how it snaps to the edges of your display(s)?
Why is Steam the only program (I know) that does that natively? I would love for ALL my Windows programs to do that (without installing 3rd party softwares/scripting).
EDIT : I’m on Win10.
I’m not sure what behavior I’m missing, I’m playing around with this steam window and can’t find it. It snaps to the edge but not in the windows way?