Grabtaxi and why are African startups locally constraint?

Grabtaxi is Southeast Asia’s only homegrown unicorn. Born out of Malaysia as MyTeksi, grown aggressively across six countries in three years. Raised $340 million.

Which brings me to the question, why are African startups so locally constrained to their country of origin, when there is so much untapped opportunity across the the continent? Lots of African startups focus on issues common to any individual/companies on the continent but don’t seem to take advantage of this. Started seeing breakouts exploring Pan-African mindset within their first/second year of operations. Know Everyone got their opinion on this, just a little bit more insight would help.