I disagree with the premise. If I need a manual or, egad, training to make basic use of desktop software, I consider it failed. It may not be the norm on this site, but elsewhere in the world users don't read documentation.

What I do expect to turn to a manual for are particularly complex operations, like multi-layer multi-step image manipulation or writing a spreadsheet macro -- operations that by and large do not and probably should not have a Web app counterpart.

This is because network latency, non-standard UI and other concerns make the Web a pretty crummy environment for complex software operations.