Presumably, this is in pursuit of making web pages behave more like apps, but it is truly frustrating. If I wanted app behavior, I'd install an app (even something like Chrome's apps). While I'm in a web browser on a web page, I expect to interact with the web browser primarily and the web page through the browser intermediary.
The Line of Death discussion is highly relevant: https://news.ycombinator.com/item?id=13400291