Linux

Yes kinda? It depends a lot on the system. It's still pretty common, even with containers like docker, for different services to run with different accounts and permissions. Eg. If you have a webapp with a small database or something, the web server will be www-data or whatever and the db will be a different user account like a postgres user or something. Even a fresh Linux install will have a separate user account for things like ntp (or systemd-timesync) etc. Users aren't usually people, they're daemons with limited scope and rule of least privilege.

Even if it's all docker containers and you deploy them with the same docker account on the host, there are almost certainly a bunch of different accounts inside.

That way if there's some vulnerability in ntp or something, an attacker might have permission to mess with the time but can't, in theory, take over the whole container.

I think there is a trend towards caring less about that aspect of defence in depth if each service is in its own container and just rely on isolation. People are deploying services running as root with ansible or even just in dockerfiles, and not caring about it because there's nothing else on the box for an attacker anyway. If they compromise the service, they've already got what they want.

I get the thought process but it still doesn't feel good to me. If some docker bug shows up that allows a container user with root to break isolation and use the shared kernel to pivot to the host or other containers, then that one dodgy webapp that's not running as a restricted user can become a part of a larger kill chain. It's really easy to develop systems with least privilege in mind and there's not much downside to doing it. It's a good habit to to create different accounts for different services (even if there's one admin/docker/ansible/whatever account for deployment).