Most are lesbos because they are too ugly to attract any man, and lesbos tend to have much lower standards.
There's that, too. Many women are very status-conscious, and would rather be without a man than "settle" for a man that their friends would laugh at them over. Going lesbian side-steps the issue.
Becoming part of an alpha-male's harem is another way to side-step the issue. Have your friends impressed by this charming guy who's going out with you. Just don't tell them that the guy is only going out with you when his primary girl is unavailable or he's dumped her for being too much of a drama queen.