Not the only reason, but it is a reason.
Whenever there's a discussion about aerodynamics, I'm reminded of the episode of "Cabin Pressure" when Arthur asks how aircraft stay in the air and Douglas offers the standard explanation about the air having lower pressure on top of the wing than underneath. Arthur's response is "So how do aircraft fly upside down?"
Whatever flight control you operate on an aeroplane gives rise to one or more secondary effects. The rudder is itself a "wing" and gives rise to a rotational force on the aircraft. Through yawing the aircraft it forces one wing forward with a corresponding retrograde movement of the other to create a rolling motion. On a swept-wing aircraft, one wing now presents considerably more profile to the airflow than the other, and in all aircraft there is some blanking of the "trailing" wing. But of course the "lifting" wing has more drag than the other. All these factors and more (eg di/an-hedral) combine together to give the aircraft its own character and relative stability.
(Incidentally, many lives have been saved through the use of secondary effects after primary control was lost (eg Sioux City DC-10).)