“The kehillas that have this restriction tend to live in cities or self-sufficient towns that people are within walking distance to many necessities and have school busing and modes of public transportation.”
I imagine that they have larger families so that the housewife has enough to keep her busy at home.
Although I do have to agree with the OP’s questions. There seems to be an incongruence between the reasons given for the ban and some of the results of the ban.