The trouble is there are perfectly valid reasons for using the older operating systems especially in the cases like hospitals.
Let's say, as an example, there is an ultrasound machine that was based around Windows XP. I know is sounds odd but there is a case to be made for taking an existing laptop motherboard design and tweaking it to add the special hardware needed for the ultrasound. Especially as the images can be sent to a central file server.
Now, 4 years later, update the OS.
Can you guarantee that the drivers for that hardware are available? Can you - as a user - update the OS on that hardware? Can the IT guys? Does the company support that hardware any more or will an update require buying a new machine?