Ideally you want the OS to be updated, because old OS are vulnerable when the computer is networked. In fact most IT departements require every PC to have an up to date OS.

It’s not always a matter of bothering - many applications are customized and made for a specific purpose. An application could have been sold to only one company as a one off. Want an update after 20 years? Sure, after paying another invoice, provided that the developing company still exists and is still willing to support such old tech.

It is just a given that many companies are stuck with some old software somewhere in their process. That explains the policy for Windows.

Windows: “if we stop shipping this 25 year old library 5% of corporate users will experience problems which will cost us money and reputational damage, so we keep it compatible.”

Linux: “we are going to replace X with Y because it is better. Things will break and it is up to the community to solve it.”