The problem ist that yes, most customers could have easily upgraded in the meantime and those who didn't – well, tough luck.
It's different in corporate or acedemic environments, though. The guys at CERN run Windows XP. The software for their particle accelerator was crafted and refined over years specifically for that particular institution and purpose. They can't just come in in the morning and click on "update" between their second and third coffee.
Or imagine your typical nuclear plant's cooling system shutting down, because Windows 10 has to install updates NOW and you don't know what it's gonna break…
I don't even work in such high-risk environments but even the point-of-sale stuff can't be just simply upgraded all the time. You usually run terminals with a very specific hardware in order to be able to provide repairs or exchange faulty modules over a relatively long timeframe. This is not like in the consumer world, where there's new machines every other week and people understand that that touchscreen for your 4-yr-old 500 $ laptop just isn't available any longer. Your customer bought an ATM for X0,000 $, so it better run for a while or they'll take their next business elsewhere.
Then there's the software. Sure, your run-of-the-mill office products will run fine on anything. But highly-integrated, specific software? Sometimes it's not even about money, you just can't get an alternative. The best and most reliable POS software I use needs SMB1.0. In fact, I'm required to even turn OFF SMB2.0 in order to have everything work over a network. Not great in light of the recent ETERNALBLUE attack, is it?
Then again, that's the way it is – the manufacturer won't rewrite their entire product that has grown over decades and is now ripe with essential features. Neither will others or the ones that do just aren't a viable alternative. Back to figuring out stuff by counting fingers is out of the question, too…
TL;DR: Yeah, if you could have upgraded and didn't, tough luck. But then there's lots who simply can't for one reason or another.