From the point of view of xmpp development, it is always connected. Thing is, xmpp session start is a very costly operation. Desktop generally does it once and

From the point of view of xmpp development, it is always connected. Thing is, xmpp session start is a very costly operation. Desktop generally does it once and has it easy from then on. iOS device connects every time a user opens an app. By the time it'll finish receiving presence information, a user will already close it, and the OS will terminate app process.