The offline installers literally are the files to install the game.

It's as close as we can get in this day to having the disc and installing from disc long after the publisher was bought out and absorbed so many times nobody truly knows exactly who owns the rights to the game anymore. As long as your disc (in this case, offline installer) was stored safely and is still readable you can install it on a compatible computer (and that's often the harder part is finding a compatible computer!)

You are just ignoring that the installers can be downloaded and saved. Or even just the game directory can continue to work.

For people who value that it is a difference. Even how the game works is different with how some don't work offline or lose ability to function offline once verification expires compared to non DRM counterparts.

You are an idiot acting as if DRM and DRM free is the same as though some license terms is the only determining factor.