There are two aspects to the idea of the father or husband being the covenant maker in the following passages.
Behold, I have set the land before you: go in and possess the land which the LORD sware unto your fathers, Abraham, Isaac, and Jacob, to give unto them and to their seed after them. – Deuteronomy 1:8
But if her husband disallowed her on the day that he heard [it]; then he shall make her vow which she vowed, and that which she uttered with her lips, wherewith she bound her soul, of none effect: and the LORD shall forgive her. – Numbers 8:30
In the one case, we have God making a covenant. Just like with Adam and Eve, God came to Abraham– not Sarah– to make the covenant. He came to Isaac– not Rebekah– to confirm it.
He went to Jacob– not Leah, Rachel or a handmaid. He went to David– and I don’t have enough space to list all of those wives! God chose his order, it’s not something that I or any other man selected. He went to the man and made covenants with those men and their generations. It is true that the Messiah would be born of a virgin woman, but in every other case, God dealt with the head of the house.
The second is in regards to covenants that people can enter into. We find that in Numbers, there is a provision that an agreement that a wife entered into could be broken by the husband within a certain time limit if he decided that it was not wise. In our culture today, there are laws in place that anything you sign (especially to go into debt or other purchases) have a fixed amount of time that you can choose to get out of the arrangement. In this case, the sole responsibility for making sure that covenants were entered into responsibly was with the husband.
Although the Proverbs 31 wife did a lot, the husband was the one who was responsible for what she did and had to actively take that responsibility. It was he that would have been the target if something went wrong, not her.