It's true that in personal computers there might not be as much usage of users as in a multiuser computer or a server. But without root access a virus wouldn't

It's true that in personal computers there might not be as much usage of users as in a multiuser computer or a server. But without root access a virus wouldn't be able to affect system files, so it would have much less persistence and would be much easier for it to be removed, even automatically by some built in or third party antivirus. Or, it might be possible to just remove it by making a separate user, and accessing the files of the older user from a folder. In personal cellphones, also, there's heavy sandboxing, so in an OS like android, there would be a big difference betwen root and app compromise, if you don't get root you are only able to access the app data of the app you compromise. Similar in Mac I think, but I'm not an expert, each app is isolated and a process from one app can only access its own data, escalating to root would allow affecting files of other apps. But we are talking about containers, so in all likelihood this is about either servers or server developers, which make heavy use of separate users for even single use stuff like an HTTP server, whether manually or automatically, run 'apt/yum install apache2' and you'll see how it creates a separate user automatically. Yes, root still matters.