What is "Install Again"?

If something is already installed what does it mean to install it “again”? If I have a light switch on my wall in the “on” position I can’t turn it on “again”; I would first have to turn it off. Then I can turn it on.

Maybe this is just a translation problem from German to English but I don’t understand the use of “again” syntactically. What’s a situation where someone would install something “again” without first un-installing it? But if I uninstalled it, why wouldn’t the button just say “install”? Is it because there’s retained-state between two separate installations, so a second install does something different from the prior install? Or is there a limit to the number of Install/un-install/install-again cycles I can do? Or is “Install Again” equivalent to “Update” where it installs a newer version?

I’m new to Cubase but I saw a thread - Cubase 11.0.30 Maintenance Update Available - #3 by maggie about a recent update where everybody was complaining about what a confusing user-interface this product has and one user had my exact same confusion:
" More specifically, the download succeeds and so does the verification step as I get I get a white tick on a green background in the progress bar. However the button text is ‘Install again’!? What?"