It's funny to look back and think about how my friends and I used to have to make sure our parents weren't home whenever we wanted to have a D&D session. You might not remember it but back in the 80s and as far as the early 90s, Dungeons and Dragons was seen as "Satanic" and as "dangerous to children" and many parents biggest nightmare was finding out that their kids secretly play D&D. Which is ironic because that was precisely the reason why we would play it in secret, Because we didn't know if our parents would freak out or not.
Also, you need to realize that there was no internet back then and there were only a handful of shops that would sell the Player's handbook or the Monstrous compendium, So when my brother was able to get his hands on these, we would lock ourselves in our rooms and study them in depth for hours. I don't know what my parents thought we were doing in there, but since it was the 1980s, they probably didn't really care.