Because it would provide a better product for your users, which is the whole point.
It also shouldn't be hard to do. A senior engineer that can't easily jump on new technology stacks is not a senior engineer.
> But that isn't why I'm running it. I have a web browser open every minute I'm using my computer, so it's already there. The browser is a multitasking application itself, so using it for music streaming fits in great. I haven't used the Spotify web player, but Rdio has been web-based from the start, and has been great.
An arbitrarily resizable browser window/tab that looks like every other browser window on my desktop, which can't share state between multiple windows, and can't interact with my desktop in any meaningful way, doesn't use native components, goes wonky if I reload, and goes away if I have to restart my browser.
That doesn't make sense. This makes sense: http://www.pandabarapp.com/