On the other side of IaaS, or perhaps in parallel to it, is the concept of PaaS.
Platform as a Service is almost the logical continuation of the virtualization of infrastructure, abstracting one level further and asking the question "why are we asking our users to spin up a server for PostgreSQL, when we could just spin up a PostgreSQL instance?".
Yes, there will always be a server somewhere, that's a given. These services don't just run ephemerally atop a CPU that's floating in a room full of mist somewhere (despite that being a cool mental image), but the critical part of this philosophy is the idea that you don't care.
Realistically, you don't give a damn about the OS your database is running on, as long as it's actually running and isn't about to crash. However, as an administrator in the past, you...
