Ask HN: Why do Apps use sound FX and websites don't?

In it's Geocities heyday, web pages often had sound loops, WAV files and horrible flash files with sound effects.

Then we all got quite sensible and realised sound effects on websites are pretty annoying.

But with the advent of iPhone & Android apps - see this beatiful Pastebot example: http://vimeo.com/8157582 - coupled with a blurring of the lines between the UI of desktop and mobile apps, are we going to start seeing (hearing!) tasteful yet complementary sound effects on websites?

If not, why not? What makes a website so different to an app in their appeal of sound effects?