I have heard from some people that having a reputation as bisexual has increased their prospects with women. I suspect this is dependent on location, social circle, and attractiveness.

It may also be that a large percentage of women are no longer interested, but enough of the women that remain are significantly more interested- and so you go from, say, 20 women who might date you to 10 women who might date you, of whom 2 want to. Overall prospects down, but easy prospects up.

(I will comment, though, that this probably has to do way more with the masculine/feminine balance of the people in question than their sexual history or orientation.)