I believe that is true, to an extent...a very small extent. I am married and I believe that a marriage is a partnership based on many levels. One of those partnerships is a "business-like" one, so to speak. Let me explain. I depend on my husband to do what he says, when he says, and respect our union. These are agreements that are implied, so to speak, and they are generally the basis of marriage vows. As a husband, he has an incumbent duty to protect our family, our finances, our future (so do I, but right now we are talking about "husband"). A marriage can be considered the "ultimate" of partnerships, in so much that some aspects of your life literally depends on your spouses compliance and cooperation (I know this sounds static, but it's the truth, LOL).
Now, if I have a suspicion that my partner is cheating, do you think if I ask (ASKED) him that he's going to tell me? Well, he won't (and did not). I have a VESTED interest to use whatever device necessary to separate fact from fiction. With children, bills, assets, liabilities and my time and livelihood invested I NEED TO KNOW. I don't need to guess and start wondering if maybe something is wrong with my ability to trust. Maybe what is really wrong is HIS ability to be TRUSTED. If you know your spouse like I know mine I knew before I looked he was cheating. But you know what, cold-hard evidence trumps a gut feeling any day of the week.
When you confront a cheater and say "I feel like you are cheating on me", you can come off as emotional and accusatory. Guess what, I'mma skip that scenario and come with the goods--You ARE a cheater, BRO, and this is how I know." You are right, you can be straight and ask, but will your mate be straight and tell? It's just not likely.