In fact maybe the reason girls don't generally have an interest in football is because
1. NOBODY ASKS. If you're of the male sex it is assumed that you enjoy the sport but it is highly unlikely that a male will approach a female to discuss such topics. Thus, how are you to know whether she enjoys football?
2. It is still sadly a very male-dominated atmosphere in which the high testosterone levels and pack mentality leave women susceptible to sexist jokes and sexual abuse. It can be frightening to be the only woman present on the concourse.
3. Although not always the case, women are often smaller and naturally weaker than men, the experience of being crushed between burly blokes while everyone scrums to get through the turnstiles is both unpleasant and potentially dangerous.
4. It is assumed that we take an interest in football for the purpose of finding a mate. It somehow seems more appealing if a woman is able to critique the substitutions made at the last match and so we get accused of trying to be attractive to the opposite sex or perhaps, as you suggested, because we find the players attractive. This is degrading and humiliating
5. As there are many men who do not have an interest in football, there are women who genuinely have other interests and hobbies in life - it is not an essential component to life.