I have trouble believing that this is the fault of the techie lobby, considering that said lobby otherwise has no meaningful accomplishments under its belt. My explanation would be that the web is massively successful because it enables user to navigate safely without being in danger of leaking their files. If a user isn't willing to install an app to do a task, it is precisely because they fear that such an app will be able to do unknown damage to their computer. Allowing the same thing of web apps eliminates their advantage and endangers users.