Nowadays almost in all f the households both spouses are in paid employment. But there are some families where (mostly) it is the wife who runs the household and takes care for children and the husband is the only breadwinner. There is a problem that a housewife is not paid for doing the housework and additionally, she has no rights for getting her retirement. If the husband dies, she is left without any sources to survive.
Additionally, such a person is fully dependent on the earning spouse. It is also possible that one of the spouses earns a fortune, and the second one receives only a survival salary, so establishing a separate account simply does not pay for both. First person cannot contribute more money, however, he or she could, and the second one cannot afford to fill the limit.