i would agree, that often cheating is often borne from lacking a perceived need. a lot of people i've known who cheat are those who are accustomed to a great deal of "attention", validation, or behavior that wanes, and a surrogate or substitute is found who meets those needs instead--whatever that need is.
but as others have already said, i think there are several reasons people cheat.
one that i've witnessed much is i believe to be, quite simply, a combination of poor impulse control (or lack of self discipline) while placing themselves in an environment that would be unwise in the first place, and finally cheating because they believe they can do it, get away with it, and nothing will be discovered, feelings won't be hurt, and no one will be affected.
for most of my career i've worked primarily with men, and often found myself travelling very often, mostly with married men
seeing the behavior of these guys (who truly seemed to appear to love their wives and have "solid marriages") when they were far from home and opportunity to cheat was readily available has shaped a lot of my opinions about the importance of making good choices that prevent you from being in a bad situation -- fleeing sin by making the choices before you find yourself in having to suffer the consequences of your bad choices, and lie in the bed of your own making.
not to mention how comfortable i'd feel about being married to someone who travels alone for work, often. and i don't think this is a "men only" scenario, just what my personal experience was.
i would refer to the above is the opportunity-associated, serial cheater, who is more driven by what s/he can get away with in a circumstantial opportunity.
and i think there are also cheaters who disinvest from their relationship and essentially move on to another person, instead of sticking with who you've spoken your vows to and committed to the health and preservation of the marriage above other, less worthy pursuits. rather than officially leaving them, they leave, emotionally and otherwise, and ignore the impending collision.
finally, i think many people fool themselves in the thinking that they can handle many challenging priorities and accomplishments. the fact of the matter is, everyone i personally know who is in the demanding, successful career hasn't had the successful relationship/marriages, aren't excellent parents, serving in church and growing in their faith, and so on. i am not saying it can't happen, but i personally haven't witnessed it.
i'm tired of people acting like we, as Christians, as women, as balanced people can have and manage everything. it's a fallacy. how you spend your time, and your energy is where your treasure (and priorities) will exist. and so to me, often cheating is a symptom of relationship neglect. and i don't mean, neglect on both sides. you can't build a great relationship alone.