Hi and welcome to the board.
My opinion is that most people are bi. Cultural conditioning causes many to not be in touch with their desire for same sex partners. So, being gay or completely straight is more rare in the culture in general. And therefore in the poly culture as well. (Of course, some people really do fall on the completely straight or gay sides of the spectrum.)
I was watching an interesting show on TV recently on ancient Sparta. It was an extremely gay-gentric culture, so the opposite of ours. Men were taken from their mothers and sisters at age 7 and thurst into an all male environment, taken under the wings of men, and expected to be mentored into the military culture by an older man who also becomes their lover.
At some point each man was expected to take a wife to breed. The wife would have her head shaved, be put in a room in men's clothing, and her husband would first have sex with her in the dark, get it over with and hurry back to his male friends and lover. The show said these furtive relations could go on for months or years. Some men who actually enjoyed being with a woman must've felt like oddities!
Nowdays with gender reassignment becoming more common, I run into dykes who have to deal with realizing their female lover is actually a man, or women who IDed as butches realizing they are actually men. This can throw ya! Some continue to ID as lesbians even tho they are now having relations with a member of the opposite sex.
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
Mags (poly, F, 61) loving miss pixi (poly, F, 39) since January 2009, living together since 2013
In a newish relationship with Steve, (33, poly)
"Master," (mono, 36), miss pixi's Dom for 3 years