[I hope I do not seem insistent and nagging like... I actually am
]
There is of course a good reason behind it. You should almost never start an activity while your app is in the background. The user doesn't expect it.
I think to cases like this:
1) my app is in foreground, Main activity;
2) I answer to a phone call or anyway I open a different app;
3) meanwhile a service of my app receives a msg to send to a second activity of my app;
4) I return to my app and now I would like that the second activity will be bring on foreground, to show the msg; instead the Main will be displayed and the message will not be displayed (of course I would find the way to save the message and view it later, but this is just an example that has nothing to do with my projects)