For me, its the need for variety.
Adding...
Variety, Variety, Variety
That's why and always will be why.
For me, it wouldn't matter that you gave me great sex every day
and that your BJ's were the best I had ever had. Eventually
they become the "Same" great sex and "Same" best BJ every day.
For me, having sex often enough was great, for about the first 3 years
of my marriage, then it got boring, even though it was "FANTASTIC SEX!"
So I got a GF and we had great, and different sex everytime I went over, but
it was the same, different sex and then that got boring so we broke up. I
found someone else for more great and different sex for a while then that
got boring and we broke up. Then I got back with GF#1 for a while and
the sex was great again because it was relatively new again. Then we broke
up again because, yeah, it got boring again. We did this about 6 times
over 18 years. Me and GF#1 are presently apart, she says for good, because
he can't handle the break-ups.
I now have GF #5 (GF's #2 - #4, went the same way as #1 but much faster) and
it hasn't been long but I see the "BORING" signs already.
In between all of the above I filled the gaps with first, Dancers, then MP's,
then SP's. It was all exhilarating at first until event that got old and
I moved on.
I love my wife and there are things she does to this day, after more than 20
years of marriage, that melt my heart, but sex isn't one of them. She has
even told me she is not interested in sex anymore. That would/will be
my defense if I ever need it.
The moral of this story is that most men have a short attention span while
women are quite possibly the opposite, what a revelation, men and women
are different!
I would say that if women (you can tell your friends this too) want to
attempt to stop their men from cheating (or whatever you want to call it)
then change it up between the sheets a bit and do that often enough
that he doesn't know what he's gonna get when he gets between the
sheets with you.