This rule is to make sure that the main players don't miss on their club matches very often. With the women's teams, it is not necessary to apply this rule, as their club schedule is not very hectic. FIFA doesn't gain any profit from the football tournament at the Olympics. However, they have allowed it in order to spread the popularity of football and to increase the funding from various government agencies. The same approach has been taken by sports bodies such as FIH, FIBA.etc. However ICC (governing body of cricket) has taken a different approach and they have refused to include cricket in the Olympics. ICC has stated that they are not interested in spreading the game and inclusion in Olympics may cause monetary losses for them.
I do not think it is so much about women's schedule being hectic or not. In men's team,,, the academies and youth structures are already well developed, but this is not the same for women's. So if you do not have the senior women playing the squads are technically very weak. They will need time and many years to get to a better quality but until then, we will see very "old" women playing in football for Olympics as they are still able to bring skill and experience.
