Your comments

Many oppered for an exit button, so i don't understand why there isn't any.

When i use Xii radio app and listen to a few stations and want to close Xii after that, you have to tap a few times on the back button for closing it down (return to the app drawer). After using Xii and start a cleaner app, i see it is still running in the background. When i use the memory booster and junk file wiper with a cleaner app, Xii opens/starts his player on my phone screen......strange?!

So, an exit button that's closing the app completely would by fine in my point of view.