I saw in my old line of work that most business over a certain size just have a few key programs that need to work and could not give two shits about whatever new OS was out if it could not run those programs. The fact that in places like the banking sector many of the programs are UNIX era and need emulation just to use on a desktop and not being spied is often a requirement it would make no sense what so ever to upgrade. I have also seen an uptick in Linux and Mac workstations as both are looking more attractive then the wild ride windows has become.
Oh and in case people think security on older OS is a concern for companies I know for a fact that several ATMs in north America are still running on XP (upgraded about 7 years ago from 2000).