I struggle to see a reason why all software is not portable as it used to be in the good old days. Under the current regime the system becomes more and more clogged up with unnecessary junk over time. It makes more sense to me to try to make software self contained with all the dependencies isolated together in one folder.
No I don’t keep the browser on a USB stick. I can see now that tools which expect all software to be installed into windows may have a problem finding software in other folders. On the other hand since were talking about antivirus software it would seem naive to write antivirus software which assumes the virus will only be found in a folder registered with the OS as an application.