There's the pricing factor too... a population with a median income of between 2 and 10% of US median income simply isn't going to buy SaaS subscriptions in comparable volumes at comparable prices to US companies. For much the same reason, these consumers are also worth less in raw money terms to advertisers. which means a lot less revenue for typical Y-combinator startups in African domestic markets even before transaction costs (quite possibly higher?) are taken into account.