Why do so many female celeberties claim they are bisexual?

I recently read that LadyGaga was vacationing with her boyfriend, but not long ago she claimed to be part of the LGBTQ minority because she is bisexual.

I appreciate the fact that she is doing so much for queer people, and I am sure she is not claiming to be bisexual for attention or for money , at least not completely.

I feel that celebrities, like Angelina Jolies and LadyGaga, should try to claim their sexuality without calling themselves bisexual when it is obvious they will ultimately end up with men and have a bunch of kids.

Do you have a problem with their use of the term bisexuality?