StephenMayes: Is there any advantage to this, over forfeiting from the menu
There is no advantage to them as to the final outcome of the match. If they disconnect and never return they still lose and it is still a forfeit. If they forfeit from the menu they lose.
For you, obviously, if they disconnect you have to sit around and twiddle your thumbs for 2.5 - 5 minutes.
So like AK said they usually do it on purpose if they are losing just as a kind of payback, i guess, for you beating on them. Its just very poor sportsmanship. Then again, i am not sure they teach that anymore, everyone is so enamored with themselves taking pics of them selves with their iphones and posting status updates about every last detail of their lives on FB or wherever else, that they could careless about you.