I work with a few places that still have 1-2 2003 servers around, and for some of them we'll probably be locking them off from any external access and doing a few other things to restrict them while still keeping them around (possibly mostly powered down except by request). That's because they're legacy systems still running old software that someone occasionally needs to refer back to - primarily old diagnostic imaging or practice management/EMR systems which are long out of support.
I have a few places that are 1-3 doctors, 3-6 staff, and they have an old system that they need to go back and refer to every week or two for things that didn't get migrated when they changed EMRs. Migrating everything out of that old system into something like PDFs for attachment to the current system would be cost-prohibitive; paying for migration ("Sure, we'll be happy to upgrade you to our new version, it'll be just like you're switching back to us, shouldn't be more than $30k or so") is the same. We long ago VM'd almost all of these systems along with upgrading/replacing where feasible, so there's not really an added hardware maintenance cost for keeping the VMs around.
And before people say "you should have migrated everything," the last migration we did, the new vendor wanted and would accept a very specific set of fields - all on a single (large) Excel sheet. Everything migrated was practice management data - demographics, insurance, etc. NOTHING clinical was migrated (possibly for liability reasons - what happens if your import of the peanut allergy info fails because of something stupid). For clinical data, the staff at the practice still goes into the old system, generates a set of reports into PDFs, then attaches those PDFs to the new electronic chart as if the customer was coming from another practice. Migrating all the patients makes no sense, this is a specialist practice where a significant percentage of patients are seen for a year or less, then are not seen again for years if ever.