Why do so many people complain of birth control pills causing weight gain? is this a legitimate issue or is the pill being blamed unjustly?

Further data: Has come to suggests that weight changes(particularly gain) are minimal on oral contraceptives. Later data seems to suggest that this is more of a perceived problem and that if there is weight gain, it's minimal and more related to fluid retention. Unfortunately, its a bit of myth going back to when birth control contained much higher doses of estrogens which can lead to increased appetite.