As a woman finds economic opportunity, even if she's only earning a couple of dollars a day, if she can save it on her phone, she then makes different decisions for her household than her husband might.
Even in our own agriculture strategy, if we got a great new drought-resistant seed and we managed to get it distributed in the system, we just assumed that it would reach female farmers. That's a false assumption, because women don't interact with agro-dealers. So if you don't develop specific programming to ensure that seed gets in a woman's hands, then the extra income [generated by higher-yielding crops] goes into her husband's hands.
In the developing world, they don't have smartphones yet. They have the older plastic phones, but women are saving money on those, because they don't have access to banks. Having that access to digital money changes everything for her because she actually doesn't have to negotiate with her husband, which she will tell you is very hard in these circumstances, especially when the means are meager. She's expected to have money to pay for the kids' health or to help with the school fees.