The men do not have enough sexual satisfaction. Infidelity occurs at the banal and sad reason: the husband loves his wife, but he can not achieve harmony with her in private life. The reasons for this are very different: a mismatch of temperaments, too strict, puritanical upbringing, his wife received, etc. A classic example - marriage Pushkin Natalia Goncharova, about the intimate side of which a very great poet metaphorically wrote in one of his poems: "shamefaced, cold, delight of my barely otvetstvuesh not vnemlesh anything." Sooner or later it will bother even the most loving and loyal husband.
Young people may not have enough home warmth, comfort. Alas, poor mistress - not uncommon among women. They always find excuses: they are working, busy with the children, but still needs to be done around the house a lot of cases. Has neither the time nor the energy! All this is true, but at least the minimum order and cleanliness in the house must be maintained. Not to mention the fact that the owner should be able to more or less tolerable cook. But if her husband regularly returns to the dirty, untidy house, but still gets heated semi-finished dinner, bought in the nearest cooking, whether it can be to blame if he starts eyeing the other women who provide home and spotlessly clean, and well prepared?
Also in marriage may lack basic similarity of tastes, habits, hobbies. The marriage was strong, the husband and wife should see each other like-minded people, like-minded people. If, blinded by passion candy buketny period of courtship, they did not see and did not understand that different in everything, now it comes up to the outside.