Working in IT in the medical field (OB-GYN, in this case), I can tell you sometimes there aren't even alternative vendors available - either one company is the only company or the others are even worse. When there are better vendors available, the opportunity cost of migrating data may be too high (What do you mean, we have to print to PDF every medical record and manually import the PDFs to the new EMR?). Even if both of those are acceptable, you're limited by your hardware: Don't want to buy another $75,000 laser for the lab? Too bad, then, because the control software only runs on the customized copy of XP. In the case of super specialized items like that laser, a modern version isn't even available, anywhere.
The joys of a niche market.