If I had to venture a guess (YUK!) it may have something to do with why women can have multiple or no orgasms where men always have only one with the same equal pleasurable experience every time. Perhaps men are hardwired to be aroused when seeing a woman aroused regardless if it’s by male or female and knowing there’s always room for them to be received and plant his seed. The phenomena of the “train,” mostly urban legend always talked about at college parties, where multiple men take turns with one woman works only one way, you don’t see it with multiple women and one man. I would also point out that by a great margin most of the porn industry’s customers are male and most women don’t like watching it much less two women kissing.
That said and feeling a need to take a shower, homosexuality is disordered pathology, anti-social behavior and rightfully shunned by society.
You have lived a very sheltered life. Every man I know has had sex with multiple women at the same time.