Absolutely brilliant and truthful observation, and as a benefit there would be far less twisted children being brought into the world if vaginal penetration was mostly brought about by loving mutual arousal. Of course this only applies some of the time, and many people won't get the message at first, but on introspection we might all see the difference between consensual loving sex and mutual masturbation for an ideal. Masturbaton is the drug that relieves but Love is the drug that heals...