system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are you prompted to close all other programs when installing something?
gpt
The installer may need access to files for a program due to some connectivity or upgrade related things and it's easier to tell you to close everything than to try and find every possible program ever made or that will ever be made that will cause instillation errors to your program. It's sort of a lazy way out of a complicated issue. 

So if your program is around 15 years but you stopped supporting it, you should tell people to close anything that may need write access.