I believe there are different reasons on why somebody is shy, not necessarily b/c One was raised only with a Mother and what not. For example, Me, I was raised with both Parents, when i was young i was really outgoing, extroverted, talked alot, as i was growing up i got Trichotillomania (Compulsive Disorder in which You pull out your hair), and little by little after time passed, that made me more and more shy/introverted.I would say when i was about 14/15 i completely changed, why, cuz as time passed, you could of seen light spots on my hair, which became bald spots in certain parts of my head and i didn't want to draw attention from anybody, though i was still very friendly and was friends with alot of people, but i was the more quiet one of the group.
So to me, when somebody is shy is because theres something going on in their life, doesn't have to be Trich obviously, but whether its cuz they're too fat, too skinny, a huge mole in their face, something they don't feel comfterable with, and are afraid of what people might think of them and all that stuff that goes with being shy...Just my opinion, didn't mean to offend anybody just incase