Yes in the research computing world (HPC and similar systems, and some other sorts of shared resource) at least. On Linux-based machines you can limit resources otherwise, via PAM, or startup of interactive sessions in a distributed resource manager ("batch system").
I've been using UNIX-like machines (mostly Linux) since the mid-2000s and single-user machines have always been the exception rather than the norm everywhere I've been.
Even at home, I've set up multiple accounts for myself (main one, one for closed-source programs, one for gaming I can share with other people…) and for my family (to each their preferences, wallpaper and so on). Having two or three user sessions running at the same time is not uncommon. I'm probably the exception here, but I don't think Podman targets the regular home user anyway.
It's not obvious to me how Podmansh would revolutionize that, but I guess it's nice, I'll try it for sure.