It is the nature of the woman.
Tell me if you are married and you love her so much and for some reason she got very sick and can not give birth and you have two options,
These options according to Islam are:
First divorce her and marry another woman who may give birsth.
Second Do not divorce your wife and marry another woman who may give birth.
Third Stay with her and forget the kids.

Let us be very vey vey honest, the woman who love her husband very very very much and she can not give birth will tell her husband to marry another woman.
At the end it is up to the husband.
Here I was speaking if there is something wrong from the woman side, also can be from the man side.
This was one reason which came to my mind.
Also imagine that a woman who is not married can do bad things or give blue jobs (Here I want to say only some women can be bad and not all women), if you marry this woman then there is a big possibility to prevent her from being bad.