Because the vast majority of the planet is straight and since you haven't come into sexual urges yet there is no knowing what her or not you are genuinely not straight, so it is most logical to assume that you are straight because youve probably never even seen a dick.

You're like 7 you have no idea what sexual urges are and definitely can't tell what sexuality you are.

THEN HOW ARE YOU SUPPOSED TO KMOW?? YOU DONT EVEN KNOW WHAT A DICK LOOKS LIKE STOP ASSUMING YOURE NOT STRAIGHT

Well blame on cadence because she taught me what it looks like

Here