That's ok at launch (to cover up how awful web apps paint). But what then? Change forms or screens and it fails again. Or hit a button - no visual indication you hit it; app hangs; screen updates in spurts.

Not all web apps, but certainly a large fraction.

Vastly more accepting of web apps. Web apps stall, spin (or worse yet don't spin yet are unresponsive), paint in embarrassing frames and masks with old content showing through the holes, and on and on. A native app that did that would be criticized roundly; web apps get a pass for some reason.