Writing applications using markup instead of platform-API-based code is so much more easier. Browser-based UI brings significant advantage of using combined teams with programmers (who generally can’t build great looking UI) and graphics and UI specialists (who can’t wire it up with the backend). The last decade of focus for developers has largely been on building to the web. The programming model and the deployment environment are all too familiar.
A browser-based application need not necessarily mean a hosted application, when a desktop runtime such as Dekoh can serve to your local browser. You have the twin advantage of a common environment for quickly building to the desktop (and web) as well as a fluent integration between the such desktop applications with existing web applications. The best way to build web-desktop integrated applications of the future.