Because dads don't always think like moms.
The possibility that your child may not be yours can cast a serious shadow over family life. Once you have a nagging doubt then your worries can grow out of control.
The problem for most guys when it comes to paternity is that it is possible to have that element of doubt. The mom’s identity is a forgone conclusion and in most loving relationships, of course, so is the dad’s. But if you have any doubt, then there are a few hints on what to do (and in some cases what not to do).
Whatever the truth, the fact that you have suspicions indicates that there are underlying problems within your relationship that need to be sorted out because, let’s face it, in a truly loving relationship, such doubts could not exist.
Lingering doubts will only sour your partnership and new parenthood, so knowing the truth is always the best way to move forward for all concerned.