In my case
Being married to my first wife, as a horny 20year old, I liked to have a lot of sex. My wife's attitude was "It's okay". But she would never tell me what I needed to do to make it more enjoyable for her even though I'd asked many times. After reading some Penthouse stores about guys watching their wives being satisfied by "Bigger" men, I began to think it was my size and not my wife.
I also liked ******** her in public. I think the part of ******** her came from the idea, that I wanted other men to see that this "Beautiful Woman" was MY wife. A way of bragging.
It took a few years, but eventually she did have sex with a few friends and neighbors. A few times I asked if size was important, and she always said "No". In asking later who were the best lovers, she would say "Ernie, and Bruce". When I asked who were the biggest, she said "Ernie and Bruce". So when I asked her if size wasn't important, why was it the two biggest where the best? She thought a moment, and then said, "I guess size is important".
I liked watching, but I didn't get to often. I did enjoy her telling me what she did with her lovers. Of all the guys she was with, only one knew I was aware of what was going on. I don't think she ever did a Black Guy, but in my mind, he would have been big and able to satisfy her better then me.
Right or wrong, that is what went through my mind.