Remember that time when the OKCupid blog claimed that most bisexuals on OKCupid were lying? Although their interpretation is highly suspect, it is based on some rather interesting data. Apparently (as of 2010), 41% of bisexual-identified people on OKCupid had only sent messages to men, 36% had only sent messages to women, and only 23% had sent messages to a mix.1
It’s possible that many people are lying, but are the numbers so surprising that we need to resort to such a conclusion? Bisexual people are attracted to multiple genders, but they aren’t necessarily actively seeking dates with multiple genders. For example, we can imagine someone who is a 4 on the Kinsey scale (”predominantly homosexual, more than incidentally heterosexual”) deciding that they should just focus all deliberate dating efforts on people of the same gender.2 Maybe if someone of a different gender came along, they would be open to a relationship, but as far as deliberately messaging people on OKCupid, it’s easier to just stick to one gender.
There are also many obvious differences between m/w, m/m, and w/w dating cultures, and differences in the social repercussions of those relationships. It is easy to imagine that a person might prefer one or the other, even if that preference is limited only to a particular time in their life, or just to the OKCupid platform.