Why do you need code injection?

Question

API

Tell me, why do many operating systems implement the mechanism of injecting code into a foreign process?
Other than a security breach, what else is the point of it?
You can update the software simply by replacing the versions of the libraries, and debugging can be done in specialized software.

Answer 1

https://ru.m.wikipedia.org/wiki/Interception_(programs...

Answer 2

to expand the functionality of existing software.
textbook example - some fraps. or punto switcher.
there were also all sorts of translators who were able to translate text in Windows windows, there were third-party window managers that add buttons to the window title, there was a lot of things.