Why is microfinance weak in Africa?

In this story from Voice of America Mary Ellen Iskenderian of Women’s World Banking discusses her organization's recent diagnostic of microfinance in Africa.

The report finds that

"...the current market penetration to low-income households is
less than 15 percent for savers and even lower for borrowers..."

and highlights high costs caused by low population density and poor infrastructure and a lack of skilled managers as key constraints on the penetration of microfinance.