So, for example, it's not unusual that, by default, your half a million USD scanner, that includes a powerful workstation to control it (the one the technician uses behind the window) will only let you write CDs (for example, to give your patient a copy of his/her scan) if you pay an additional "CD Writing license"
Now, with PACS and centralization that have changed a bit, but still...
Actually, it's not.
Some idiot will get the idea that they can just "transfer the hard drive immediately" because they didn't pay enough money on their support contract to get 4 hour response rather than 48 hour response. The dongle prevents that.
Medical devices are certified for the entire device--that includes the specific PC and the specific version of operating system running on it.
Same for a lot of other industrial equipment. In my (admittedly limited) experience, they get cracked pretty quickly by the owner, either before the factory ever gets any downtime, or right after the first time.
In the medical field, almost all software for performing and analyzing EKGs, X-rays, MRIs etc. comes by default with some sort of dongle-based protection. Apparently, it's not enough that you need the biggest dongle in the world (i.e. the machine itself!) to use the software. Some vendors do offer alternatives if you fight them hard enough but the default still is a trip to dongle town.