Why do traditional wedding vows make no mention of having children?

Here is a list Only Hindus thought to include mention of children. Could you imagine a man asking for divorce after having a child, on the grounds that raising children was not something he signed up for? In sickness and in health, and till death do us part, but nothing about kids. Put the kid up for adoption.

The wedding vows certainly seem to put a lie to the claim by those against gay marriage that marriage is necessarily about having children. The vows are as much applicable to a gay couple as a straight one.

It is of course true that people can marry without any intention of having children. An elderly couple, for example, would not be criticized for not expecting or intending to have children. Still you would think that the vows should make some mention of having children, even if only tangentially, since that is such an important part of most marriages.