It may be that she or feels that now that they have closed the deal that they don't need to any more. However, I can attest to the fact that it will only lead to the marriage breaking up. If they don't have that intimate time, as well as the intimate time during the day, a simple call, or flower, etc. One or both will wander and look for something new. It is the excitement of the chase and the conquest.
My friends wife as soon as their kid was born looked right at him and said I don't do that, I'm a mother and cut him off completely.