The answer to any question starting, "Why don't they—" is almost always, "Money". - Robert A. Heinlein

“The answer to ‘Why’ is always ‘Money.’”

“Jim, you’re a fool,”Bowles answered.
“No, I’m a bachelor. Why? Because I can’t stand the favorite sport of all women.”
“Which is?”
“Trying to geld stallions. Let’s get on with the job.”

I will accept the rules that you feel necessary to your freedom. I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do.

They were both of the extremely opposite sex and just being around them was fun.