They are dealing with a man that has never really been nor felt truly loved by his mother nor another woman.
So it's going to be hard for him to trust a woman for a long time unless you are adamant about showing him he can trust you to the fullest.
These females that are of his choice only show him what he shows them because they are too immature to understand the nature of a male.
They can't understand that men tend to run from love only because they have a dominate nature that tends to come with an ego.
And that ego tells them to refuse the woman that they know without a doubt that they love because she knows too much about him, more than he.
But god made woman from the man's rib so why would she not know you. You are what is familiar. She IS you. So why run?
God placed that type of familiarity on this earth to remind you of his love. Just to remind you how you're made in his image. And he loves, so you can too.
Its nothing wrong with loyalty but you have to trust in it and have faith that your other half will too.