This assumes people have the presence of mind to go through the settings and disable everything...
... which is not always the case. And Android phones still can't do Nokia-style sound profiles unless you install something which means nobody does.
Perhaps computers and phones could have a dialog box on first run asking them if they prefer fewer/no sounds or if they're an inconsiderate bastard.
Addendum: I need to add the Original Brian Eno Speed Windows 95 Startup sound (before MS sped it up 4000%) to my Spotify playlist somehow.