Nedarim 72: No Need to Hear Her Vow

The rabbis examine the precision of the baraita quoted in daf 71.  They wish to understand exactly when a husband can nullify the vow of his betrothed when time, silence, and/or death cloud the clarity of halacha.  This conversation helps the rabbis to underline some of the halachot regarding nedarim in general - when a husband is permitted to nullify his wife's vow, what indicates his ratification of her vow, etc.

A new Mishna is introduced at the start of amud (b).  It teaches that the practice of Torah scholars (is to ensure that betrothed women are not 'encumbered' by any vows).  Before daughters leave to be married, fathers declare that all vows vowed in my home are nullified.  Similarly, before wives marry their husbands, the husbands says "all vows that you vowed before you entered my jurisdiction are hereby nullified".  Husbands are not able to nullify past vows once their new wives enter their new homes.

Rami bar Chama wonders if this refers to vows that have not been heard by husbands - how are they permitted to nullify unheard vows?  Rava points out that the fathers might not have heard their daughters' vows either when they state their general nullification.  The Gemara disagrees, noting that Torah scholars are mentioned because it is their responsibility to ensure that fathers and husbands learn of their daughter's or betrothed's vows on the day that those vows are made.  

The Gemara also suggests that husbands might be saying that when they hear of their betrothed's vows following marriage, those vows will be nullified.  The rabbis debate whether or not these men have to hear vows to ratify or nullify those vows.  They argue that in fact it is not necessary to hear a woman's vows to be in charge of those vows.  Further, Rabbi Yonatan says that the Torah repeatedly teaches us that a person's agent is like that of himself.  Thus a father's or husband's agent can also take measures to control a woman's vows.   And he doesn't have to actually hear those vows, either.

It seems that the rabbis are very concerned about the ability for men to control the vows of the women in their authority.  I am trying to understand how this might play out.  If a betrothed girl - a twelve year old about to be married - vows that she will not benefit from her brother-in-law, let's say, for the sake of shalom bayit.  And for some reason it is important that that vow is nullified.  Why?  To simplify things?  To ensure that the new husband will not be inconvenienced or held financially responsible for the implications of her vow?