why do men cheat?

Because you're boring and I'm horny.

I think they cheat when they aren't satisfied. I think as woman we need to satisfy our men and change things up a bit, always make it interesting for them. They cheat when they get bored. Gotta spice things up.

Men are biologically driven to spread their genes as far and wide as possible. And women are supposed to be drawn to the strong alpha type who will be strong and able to protect them, and will try to attract that man when she meets him. So he's drawn both ways.
Plus in our society women are taught to withdraw sexually once they have children, and to use sex as a weapon to punish the husband if he doesn't behave in the expected fashion.

I don't buy the sometimes you just can't help it mentality either. We're not primates, we're humans and we're fully capable of controlling ourselves. It's just a matter of wanting to or giving in to temptation. If you value certain things higher than a few moments of closeness with a stranger then this isn't a problem.

However, I know exactly what you're saying above there. I know many people who were single for a while, several of their friends got married and had kids, they felt as though they were "behind" and had to "catch up", so they married the first person that came into their life. Everyone around them would wonder, what did he see in her, why did they get married? It just didn't seem right. Sometimes it works, other times it doesn't. But there are definitely many cases of people just getting married and having kids because they think that's what you're supposed to do.

The reality is, there is nothing that you're "supposed" to do in life. You can live your life however you want provided you are willing to accept the consequences of your actions. If you don't want to get married, then you shouldn't. You shouldn't do something that life altering just because other people are doing it. It's not as trivial as trying a cigarette in high school with your friends when you're a young dumb impressionable kid. This is committing to someone else for the rest of your life, and as an adult you should know what you're getting into ahead of time and weigh everything out. Even then nothing is guaranteed, things could still go south. But to do something just because others are doing it is not very smart.

I knew long ago that I wanted to get married and have kids, and I love it. But its not for everybody. I have a friend in the military who can't keep a girlfriend for more than 3-6 months, and he's so self absorbed he'd most likely be a horrible husband or father because he can never put anyone ahead of himself. But he knows that's how he is, so he stays single, and enjoys the single life and what he does for a living.

To each their own I say. I don't think staying single or getting married are necessarily the "right" way to live life, you have to do what makes you happy and what works for you. But to jump into something as serious as marriage and then throw kids into the mix just for the sake of "catching up" to your friends or conforming to social norms is a bad idea.

It doesn't have to be a choice between the free-wheeling single life and a monogamous marriage. There are lots of ways that committed, loyal couples navigate the complex terrain of sex and commitment with compassion and openness and honesty. It can be scary to talk to your partner about your sexual desires, but we all have urges for other people and we shouldn't lie to our partner about them.