Is infidelity and betrayal just inevitable?

Are there really relationships that go start to finish with no infidelity or betrayal, or is it just inevitable?

I was reflecting recently and just realized that every relationship I've been in (not many, met my wife at 22) has had some element of infidelity. I've been BP, AP or WP at one time or another. Are there normal "clean" relationships that just start and then end, or do I just make poor choices?

I don't know why I was at first surprised when I read how high the cheating rates were in Shirley Glass' "Not Just Friends" book. I guess I don't reflect much about past relationships.