Just like bridges and highways and buildings, software infrastructure needs to be maintained, too. And, occasionally, upgraded. "If it ain't broke, don't fix it" is fine, unless you start losing the ability to fix it when it does break.
Failed Windows 3.1 system blamed for shutting down Paris airport | Ars Technica
And the people who understand the old operating system are all retiring.
I don't know which is scarier — that they were still running 3.1 or that I recall so vividly working on 3.1
+The Bruce, Mile High the Hubble space telescope originally ran on an sx386. Updated to a dx486.
I still have an original box of 3 1/2" floppies for 3.1!!
lol. I once worked at a software company. They made their fortune with a DOS product, way back in the day.
It was so old they didn't even have the source code anymore. But, dang, people were still buying it.