although why this would be a better deal for women was never clear to me.
In a kibbutz, women were supposedly freed up from child rearing and allowed to work. Women and children freed up from a patriarchal structure. From Wiki:
When the first children were born at the kibbutz there were inevitably some ethical dilemmas that needed to be solved. One of these was that the kibbutz was striving for equality, including the equality of the sexes. Women were only seen as separate because they gave birth to children, automatically tying them to the domestic sphere. In order to liberate women and promote gender equality, they could not be tied to solely domestic duties and child care giving. The Kibbutz wanted to give women the opportunity to continue their work in the agricultural sector and industrial sector.[27] As such, "Communal education is the first step towards woman's liberation." Chayuta Bussel
Along with gender equality, the issue of parenting under the communal way of life was a concern. The parental tendency is to view the child as a personal possession and to dominate them. The founding members of the kibbutz agreed that this was not conducive to community life. They also thought it was selfish of parents to want to control their children and that this did not give room for the child to grow as their own person.
To solve these issues the founders created the communal children's houses, where the children would spend most of their time; learning, playing and sleeping. Parents spent three to four hours a day in the afternoon with their children after work and before dinner.
Collective childrearing was also a way to escape the patriarchal society that the founders came from. Children would not be dependent on their fathers economically, socially, legally or otherwise and this would eliminate the father's authority and uproot the patriarchy.
In the children's houses, trained nurses and teachers were the care givers. It was felt that relationships of the children and their parents would be better because parents would not have to be the sole disciplinarians. Children grew up in the community environment and grew up with children who were born in the same year as them. The financial responsibility of the children was shared by the community.