> This makes any purchase on Steam basically as safe as a physical purchase, resulting in Steam basically replacing physical game purchases on the PC.

Not entirely, since there's still some dependency on their client to put the game in 'offline mode', which requires phoning home to Valve.

A better example would be gog.com, which gives you the game binary/installer to download and no requirements for phoning home or any other shenanigans for being able to install/play it.