Another bullet point on the endless list of reasons not to run Windows Server 2003 is that it’s less efficient to manage than newer versions of Windows Server
In some organizations, computers were running Server 2003 not because it hosted a critical non-migratable workload, but because the server had been forgotten and was a data center derelict.
You’ve may have heard of shadow IT. It’s where users do an end-run around IT department policies and spin up their own servers in the cloud or use file sharing services to store organizational files. IT departments constrained by management foot dragging on Server 2003 migration can, to an extent, take matters into their own hands.
Running an OS in a production environment means that you need to be able to recover it when something goes catastrophically wrong.
Applications still running on Server 2003 are unlikely to get updates from developers.