Outside factors are not an issue.
If every role model of a programmer you see until you're a teenager is male.
If computer programmer Barbie involves the girl doing some design, but the actual coding being done by boys.
If every children's TV show that includes both women and computers has the woman saying computers are hard and the man solving the problems.
If all of the clever boys at your school are encouraged into extracurricular activities involving computers, but the girls aren't.
I'm sure it would have no impact at all on you.
If you don't think that this is real, then sit down for a couple of hours this evening and watch two hours of children's TV. Count the number of male vs female lead roles. Count the number of times anyone builds anything and whether it's done by a male or female character.