No, I don't believe it's true.
I believe people start in relationships for the wrong reasons (fear of being alone, the desire to "fit in" as part of a couple, fear that nobody else will have them being my main reasons), which can then lead to cheating as a way of bolstering self esteem, as a way of trying to escape from the wrong relationship, as a way of proving that other people wouldn't say no... Not saying it's right mind you, I don't believe it is. But most people are driven in some part by fear - of being found out, of being left alone, of change, of finishing what's obviously wrong and having to deal with the aftermath....
I have cheated and been cheated on in the past.
I have never cheated on my current DH (together 10y) and never will, although some may feel that I cheated with him (we got together as my previous relationship was breaking up).
I am less and less driven by fear, having worked through a lot of my emotional issues in the early days with DH. I have much better self esteem, I love him top to bottom and back again and wouldn't think of putting that at risk.