actual reason: money
That's definitely a big part of it.
The boring answer is that the web isn’t one tech, and neither is native. The future is far more likely to be a hybrid of many things that can’t easily be classified as “web” or “native”.
A fun test for anyone who tells you web is winning (whatever the hell that means): Ask them how they use Twitter, Facebook, App.net or their favourite social service. If they say they use a native app, ask them why.