It's a lot more complicated than that. Contrary to what some people try to claim, businesses aren't sticking with XP because they are lazy or stupid. Many people really don't understand the business aspect of this. It's not the same as a person upgrading one or two computers in their home.
Businesses have a very legitimate problem -- changing thousands (or tens of thousands) of computers to a new operating system is very expensive -- not just the cost of the OS itself but you have to pay people to do all the upgrading and deal with all the problems that come up. And after you spend all that money, what do you have? You have thousands of computers that look slightly different but work exactly the same as they did before. So what benefit did your company gain from spending all that money? This is a legitimate business concern.
Then there is the problem of software, and this is something that affects many companies both large and small. Hospitals, doctors, dentists and many other businesses run specialized software that is very expensive and, unfortunately, in many cases, very poorly written, meaning that it runs on Windows XP but often won't work on never versions of Windows. And so, in addition to all the expense involved in changing the OS, there is the additional expense of buying new versions of other software. And once again, once you've spend all that time, effort and money, what do you have? Computers that function exactly the same as they did before.
What you really have here is an inherent conflict between the software companies and the companies use use the software. Software has matured to the point that 12 year old Windows XP, 10 year old Office 2003 and 8 year old Photoshop CS2 are still perfectly fine and able to do everything that most people need. But the software companies need to keep selling software, so they keep making changes to create "new" versions.
But businesses don't want "new". They want stability. They don't want to be constantly changing things because that disrupts their business and costs them a lot of money, with little or no benefit. And the same is true of consumers. People drive 20 year old automobiles, sit on 20 year old furniture and live in 100 year old houses. They see no reason to spend a lot of money changing their computer when what they have works and does what they need.