Alot of people are actually intersex is one way or another. And in a lot of cases the person has no idea about it till they get tests done for something else and it shows up. What I mean is it's notas simple as "if you're born looking like a boy then you're male, fullstop." Obviously, that's the case with the majority, but there's a very significant minority where that isn't the case. And when you consider that we all start off the same way anyway (whether we develop to be M or F), it's not that surprising there are so many who don't fit into categories they're assigned