Unfortunately Bisexuality is never a simple case of option A vs option B. Not only does society view Heterosexual and Homosexual relationships differently but shapes them according through the individuals in each relationship who tend to act differently as well.
If only dating another girl worked like dating a guy (and vice versa) then same sex relationships and bisexuality would probably be more common but largely they just seem to be a hassle and in the end are more trouble than their worth.
Besides, most people who say they're bi are just admitting that if the circumstances were right (i.e. drunk) they might consider having a fling with a hot member of the same sex, but never a relationship. You have no idea how many times I've been duped into situations with other girls who just wanted to show off for their boyfriends.







