One must be able to survive, move on, and be happy. Divorce can leave a man in near destitution. The courts have turned marriage into a high stakes gamble wherein the man stands to loose the most in the vast majority of cases, even cases wherein the woman is the reason for the divorce. This is because most states are "no fault" states that do not establish fault. They simply divide all assets and entitle the wife to a percentage of his income and retirement as it relates to spousal support and child support. This is why so many men don't want to get married.
Civil marriage offers a man no real security.
Those men who are in unhappy and/or sexless marriages have no real choice but to commit to a life of institutionalized celibacy, seeing their wife as a merely a room mate, or have an affair. It's sad, but true. Ideally our love for God should keep our marriages alive and happy. But being human, this isn't always so. And ideally if it is so, a man should be able to live celibate in the marriage if only for God. But the spirit is willing and the flesh is week. It is not good that a man be alone. Most men will instinctively seek a discrete physical relationship on the side if given enough time without physical intimacy from his wife.
It's all sad but true.