Applications still running on Server 2003 are unlikely to get updates from developers.
It’s not just support for Server 2003 that finished a few months back. Vendors are unlikely to support applications running on OS unsupported by the vendor.
Just because you can run Server 2003 on current virtualization platforms doesn’t mean you’ll be able to do it in the future.
Running Server 2003 in the cloud is an increasingly hit and miss proposition.
Many server administrators have the same enthusiasm for policy that a 9 year old has for the visit to the dentist.