There is more to that problem: Nowadays everything has to be online. (Mass) multiplayer! Singleplayer? Boo! So 1990s! When a good portion of a game is online, it means having next to nothing when the servers go down. Generally I agree with you: The current implementation of the download business is flawed and anti-consumer (and WILL shift towards Mega-DRM). So… will not buy!
On the other side: At some point hardware WILL fail. From that point of view even NES games will get lost even though you paid for them. DSi/Wii Shop went down – purchased content still available. Backup is mandatory.