My father's computer is running Vista. I tried to upgrade him to Win 7, but lack of drivers for his Samsung laptop meant that his USB dropped to USB 1.0, no drivers for his printer, no drivers for his scanner, and no drivers for his wifi. The color calibration system he uses wouldn't work on Win 7. Upgrading to Win 7 also forced him to upgrade his Creative Suite, which then wouldn't support the RAW format on his very expensive DSLR.
This isn't just a matter of "clinging to old technologies". To support high end photography, he buys expensive cameras, scanners, printers, color calibration systems, and more. Upgrading isn't just an afternoon of work. It would involve throwing out thousands of dollars worth of hardware and software, and starting over.
Businesses run into these kind of situation all the time. Multiply it to thousands of employees, and the costs can be staggering.