The reason for this is that you are trying to use an IntentService. Here is the line from the API Docs
The IntentService does the following:
Stops the service after all start requests have been handled, so you never have to call stopSelf().
Thus if you want your service to run indefinitely i suggest you extend the Service class instead. However this does not guarantee your service will run indefinitely. Your service will still have a chance of being killed by the kernel in a state of low memory if it is low priority.So you have two options:
1)Keep it running in the foreground by calling the startForeground() method.
2)Restart the service if it gets killed.
Here is a part of the example from the docs where they talk about restarting the service after it is killed
public int onStartCommand(Intent intent, int flags, int startId) {
Toast.makeText(this, "service starting", Toast.LENGTH_SHORT).show();
// For each start request, send a message to start a job and deliver the
// start ID so we know which request we're stopping when we finish the job
Message msg = mServiceHandler.obtainMessage();
msg.arg1 = startId;
mServiceHandler.sendMessage(msg);
// If we get killed, after returning from here, restart
return START_STICKY;
}