I've got a theory about this.
I know a lot of female readers who have switched to male/male romance, not just because two hot men are better than one, but because they're finding het (male/female) romance boring. Not that the plots are slow or the same or whatnot, just that they don't care that much if the couple get together.
This is my theory: Sex ruins suspense.
Back in the day, love really was a battlefield for a female. Examine Jane Austen's stories carefully - there's a lot of quiet desperation there. If a woman couldn't find a husband, she was doomed to a life of dependency on the kindness of others--family, friends--and that often meant poverty.
She couldn't introduce herself to a man (a mutual acquaintance was required) and if she tried seducing a suitor not only her reputation but the reputation of her entire extended family could be ruined. She might be shunned socially, cast out of her family, and end up dying on the streets.
Single-motherhood was practically a fate worse than death, right up to the last few decades of the 20th century. Families that could, hushed it up by sending the woman away - saying she "went west for her health" or some other months-long, far-out-of-town vacation where, by the virtue of distance and anonymity in a new area, she could secretly give birth and give up her child.
Love, romance, marriage - these were life and death decisions for a woman. There was danger involved.
This isn't the case any more. Women need men like a fish needs a bicycle, right? ;)
A single woman can have everything on her own--a career, a child, her own place in society, success, happiness. She can have sex with whomever, whenever.
And since sex sells, the heroine is often required to have glorious sex every other chapter.
However, if you have a romance book where the conflict is:
The sex is fantastic but do I really love him? You don't have any urgency. It's mundane. There's no danger anymore.
With male/male romance, the love itself is the danger.
Just by existing, it could threaten the welfare and future of the men involved, and their families - and extended families if the book is historical. In fact, the mere love itself could lead to jail time or death--right up to the last few decades of the 20th century (and even later).
So with m/m romance, the reader is actively engaged in cheering for the couple to succeed, hoping that, against all odds, despite all the blocks society placed in their way, they find their Happily Ever After.
There can still be hot sex, but many readers like the Forbidden Love aspect best. The longing looks. Breathless meetings. Fleeting touches.
The way het romance used to be written.
So anyway. That's my theory.
And the fact that two hot men are hot. :)
