I thought this was ironic too. This assumption that only a man would be interested in football, is like a woman going to buy a car and only being shown the vanity mirror, because clearly only a man would interested in the rest of car.
Imagine you're the CEO of a tech startup, in a meeting with some Wall Street people. You look like Mark Zuckerberg, they're the "captain of the crew team" type Wall Street likes to hire. They ask you: so, what sport did you play in college?
Sometimes questions like that are an attempt at signaling exclusion. The purpose is to remind you that you're different from the group. It's really irrelevant to the quality of the question whether you were actually the school's star track athlete, or instead spent all your time hacking on your computer. It's even irrelevant whether the stereotype is actually true (I don't know if people at tech startups are less likely to have played sports in college than people at investment banks). All that needs to exist is a clear stereotype and for both sides to be aware of the appeal to that stereotype.
