But the goal is not to do everything that native applications do, but instead provide features to users. Here's an example: lets imagine it's 2005. You have a n

But the goal is not to do everything that native applications do, but instead provide features to users. Here's an example: lets imagine it's 2005. You have a native application that stores 1 GiB of data to the disk for caching of media assets. Now you would like to reimplement that as a browser app, but there's no browser API for disk access. What's the solution? You could provide a browser API for direct arbitrary disk access, but that's clearly not secure enough. Instead, File API was created with a lot of restrictions compared to the api that the operating system has. If you think it this way, you can go extremely far in replacing native applications. I guess the core problem is that OS APIs were not designed to execute unsafe code, but browser APIs are. Ultimately, there's no application-level feature that couldn't be implemented with a well-designed browser API. In addition, I like it that browsers are creating new APIs relatively slowly. The reason is simple: security is difficult, and there's time to actually think about security issues.