It is not only attributable to fraud, but just the clunky nature of VIsa/Mastercard payment processes. For example, I am in the middle of disputing a 2 month case for a double charge on my Mastercard- Nakumatt prepaid card. I wouldn't recommend this experience to anyone and I can see why Kenyans are averse to prepaid cards.

They have their use in retail malls and retail chains, outside of that is a stretch in their present state IMO.