So what is tricky about this? Global install is cp -r */ /usr inside the downloaded release folder. I'm probably still missing something.
With apps, same story, it ensures everyone has the app.
Install via cp -r / /usr is not a good idea as the package manager has no idea you are doing this and won't help you out.
In a worst case, the package manager will trample all over the install.
Additionally, a simple cp -r / /usr will probably not set correct permissions automatically, which means either users can edit the binary or won't be able to execute it.
Lastly, it means any update will have to be installed manually for every single release.
Package managers do this automatically and with much less friction.