Multi-user clusters are still quite common in HPC. And I think you're not going to see a switch away from multi-user systems anytime soon. Single user systems like laptops might be a good use-case, but even the laptop I'm using now has different accounts for me and my wife (and it's a Mac).
When you have one OS that is used on devices from phones, to laptops, to servers, to HPC clusters, you're going to have this friction. Could Linux operate in a single-user mode? Of course. But does that really make sense for the other use-cases?
When you have one OS that is used on devices from phones, to laptops, to servers, to HPC clusters, you're going to have this friction. Could Linux operate in a single-user mode? Of course. But does that really make sense for the other use-cases?