The reason why giants doesn't have male genitals. When the author was drawing the manga, he discussed with the producers whether to include the male genital in or not but then they thought, if let's say in real life a 180cm man's penis is approx 10cm, then the 60m tall titan would have a penis with the length of approx 3m... come to think of it, a giant running with his thing swinging side to side... ;O So the author decided that giants will not have male genitals.
I am. Forever. Laughing.