Elizabeth the thing is that often for men, whether it's with a wife or a hooker or whoever, sex is just sex. So whilst sex with you I'm sure wasn't meaningless to him (although even in long relationships its not a lovey dovey thing every time is it, sometimes it's just a momentary need/desire), sex with other people most likely was completely meaningless.
I think the best way I can explain this to people who don't feel the same about sex is with an analogy about food. Now, I know, it's flawed, food is need, you'll die if you don't get it, but, stay with me, because "hunger" is good proxy for sex (speaking personally). Sometimes, food is just something to kill the hunger. It's a burger at a fast food joint. Might taste good, but the goal isn't really taste, ambiance, great service, or anything other than "make the hunger go away". In fact, the food might actually be bad for you, make you feel crappy afterwards, and make you regret ever eating it when you go to the bathroom later (Taco Bell, here's looking at you), but, you still eat it because you're hungry.
Sometimes food is much more. It's a romantic dinner cooked by your spouse. It's a 5 star place with the best service and really exotic ingredients. It's a dinner looking over the beach in Hawaii. Yes, there's food there, and yes, the desire for food is still served by the meal, but the meal itself isn't really the "only thing" your after, it's the whole package you want. Take that great food from the place in Hawaii with your wife, put it in a plastic box and eat it on your way home from work in rush hour traffic and it's lost everything that made that meal great. You might still enjoy it, you might even enjoy it more if you're really hungry eating it in rush hour traffic, but it's lost everything that made that particular dish and meal "special".
Almost all the women I've ever slept with fall into the "good meal in traffic" category. I was hungry, there was food, maybe even good food available and I ate it. Enjoyed it. But it was just to fill a "need", not because I really wanted "great food", I just wanted something to eat. In fact, as a younger man, I avoided "great food" because it was too hard to get a reservation and too expensive. I just wanted a quick bite, something to enjoy "enough" and then move on with my day. And that, IMHO, is the way that a lot of men (certainly the ones I know IRL) see their AP's. They are the fast food. And yes, it's meaningless to them in a lot of cases (again, IRL, almost all of them). But the analogy holds here too, if you're an employee at MCD, do you get upset that people seem to run in, eat as fast as they can then blow right out of there when they are done instead of savoring and enjoying the meal? Well, maybe some do, but, if they do, they are missing the appeal of "fast food". And, if you look at what I said above, how much of that applies to your typical male A? "as fast as they can then blow right out".. Sound familiar? Because it's the same thing that men do in a lot of affairs.
It doesn't mean that all food is meaningless to someone because they go to MCD. It does mean, however, if they promised never to go there (as almost all do), and then go behind your back to do it, that it's a huge relationship problem, it is. I don't want to excuse the behavior, for those who read my posts, I almost all feel the man is "more at fault" in an A, and I think that WH's should bear the brunt of the fallout from an A because, in many cases, they are the ones who caused it to happen. However, this message is really to the BW's who are suffering on this issue. It's me returning the favor for all the WW's who help me (and other BH's) with the "it wasn't about sex" discussions around our WW's. Well, in this case, it was about sex. 4 hour old Big Mac, soggy bun with burnt fries sex. But it was about sex and it probably was (in EI's almost always, but even in your typical A) just a "fast food" desire that your WH was trying to fill. Yes, I do know that there are some "deep in love" twisted up WH's who don't know which way is up in an A, so, that person does exist, but, in my personal experience, that person is also rare.
I think I said this before, but, when I first came here and started reading, I found this thread and thought "This must be the place for BW's to talk". Which, it kind of is, but that wasn't what I was thinking. I thought that this was THE betrayed wife thread. Like, all of you were here (or almost all) because, in my eyes (incorrectly) a man having an A would always fit into "EI" (because that's all I'd ever seen IRL). I also think that a lot of men claim some "emotional attachment" to the AP when d-day hits because that's more likely to lead to R, even when it's not true. I think that "I didn't know what I wanted, I thought maybe I loved her, but never stopped loving you" goes over a LOT better to most BW's than "I was horny, she said yes". Even though the 2nd answer may (or is, in my experience) a lot closer to the truth than the first.