What about the benefit that the web brings to updating the user's install? I know that it is technically possible to push a new Java or .NET app out to users. I've done it. The one thing it requires is a lot of coordination. Notify the users to keep their equipment on the network from time X to Y. Notify the infrastructure team to schedule a push. Have the dev team on standby in case the push goes bad. Have the softw…
To be honest, Google takes care of all the complexity to have apps updated on Android. It's even better, because you can do a stage rollout really easily (i.e. just deploy to 10% of users, then 20%, then 50%, etc.). It's possible to do on a web app but you'll have to do it manually. You still have to push the apk and stay alert for the feedback, but you have to be careful with web apps update too anyway. I'm not sure…
Beside that I think virmundi above has his points, and I agree with him. App updates are not instantaneous.