There is a growing list of software that which has discontinued support for Windows 10 on the latest versions (or the Server versions thereof). I'm not sure if your example of running a ~16 year old version of SQL Server on Server 2016 demonstrates.
To my original post - if you only need to run an old version of a software package, then an old version of Windows is fine. Just because something is old, it doesn't mean that it is not useful.
The system runs only one app and does not serve public internet content - it does not get any updates at all, only this one app is updated every few month.
Running MS SQL 2008 R2 and MS Server 2016 in production here.
What "modern software support" do I lack here?