I think that anyone who's ever worked for anyone else who supplied computer equipment knows that you're at the mercy of your employer's decisions, and those decisions often have nothing to do with what makes the most long-term sense.
That being said, I think the question, "Why are you sticking with XP?," is directed at those who have the ability (and that includes finances, we all get forces of economics) to change, but don't. The most frequent reason I hear is a variant on, "Because that's what I'm used to." Well, you weren't when you first started using it and every version of Windows except Windows 8, which was a weird change in a lot of ways, has a very strong set of roots in its predecessors. I see that more in Windows 10 than I ever did in 8 or 8.1 - those two releases seemed to be when Microsoft was thinking about the world as if it was all touch-screen and tablet oriented and that desktop computers would be passe. Win 10 has wedded pretty much all that I liked up through Win7 with the few things I liked in Win8 as well as throwing in some very useful new stuff. My clients who have gone from Win7 to Win10 seem less traumatized by the transition than going from Win7 to Win8 or Win8.1.
At this time, barring outside forces such as the ones you're dealing with, it makes very little business sense or computing sense to keep nursing Windows XP along if you're using it in cyberspace connected environments. It's a huge security risk just do to what's not been patched for almost 3 years now in the OS and sometimes longer in the third-party software on it.
I've said it before, and not only about Windows, either, but there is a great advantage to transitioning to a newer OS not on the bleeding edge, but when there's a huge cohort doing it at the same time. Right now the ability to find Windows 10 information that's up to the minute and widely available is very high. As time goes by that decreases, and people no longer have it "fresh on their minds" when it comes to questions about what they did to get a specific setting tweaked, for instance. I couldn't tell you now probably way more than half of what I used to know like the back of my hand about Windows XP because it's been years since any employer I've worked for used it or I've used it as my primary OS. In certain respects the same thing will occur with Windows 10, too, well before it's replaced because so many things are "set it and forget it," both literally and figuratively.
Back to the subject: Third-Party developers tend to drop active support for a given OS very shortly after the OS manufacturer does. Backward compatibility may exist for a while "by chance," but it will eventually be terminated when there's a conflict between being able to create what the developers believe is an improved product that runs on a supported OS and backward compatibility.
Here is a test to find out whether your mission in life is complete. If you’re alive, it isn’t.
~ Lauren Bacall