While modern chamas have a load of weird rules, others are traditional and for a reason. Take kamweretho for instance, which is common among women from Central Kenya.
Kamweretho is a chama in which unmarried women with grown up children who are about to get married join for the sake of receiving dowry. Through kamweretho, a woman has enough critical mass of money and numbers to ‘marry herself’ so that she can receive dowry when her children get married.