Why? I don't really understand the hype to run everything in the web browser. It is slow, restricted environment.
That is true, it is realy a bit slower and the environment is restricted. If your software needs to run in native environment then web-environment is not what you want.
But also has some advantages :
Web-browser environment is preferable when you need to make application that needs to be
1. OS independent: runs on Win, Linux, Mac, Android, OpenBSD ... the application literally doesnot care the users OS.
2. Centraly maintained: desktop applications are maintained in style of "Please upgrade, download the latest version of our software". Web apps are totaly opposite, put the new version on the server and its intstantly available to all users.
See, it has it's purpose.