Maybe you skipped your adolescence and went straight to adulthood. When you're 13, you're not thinking about telegraphing your wank targets. To be honest, my dad was an old school dick. He was probably happy to see me with posters of hot women. He was more concerned that my long hair meant that I was a "long-haired faggot" (his words) and my mom thought my rock band posters meant that I was getting into Satanism. Bottom line, I didn't care what my parents thought. Frankly, if I was pissing them off, it was probably a good thing.