The movie itself is generally encoded at a higher bitrate than what you can find in streaming or torrents.

The media includes bonus features that generally aren't available in streaming or torrents.

The media will not suddenly stop existing if some server breaks down, some company goes under or some contract expires.

The movie will not suddenly get "patched" with an AI-upscale or censored scene one day while watching it.

You can lend the media to someone else to watch without having to ask for permission to anyone else.