Why can’t newer money transfer services (like TransferWise/Wise and WorldRemit) send money from some emerging markets where demand exists?

The reason is not why these new money transfer operators are not able to send money out from these emerging markets because they are new, it is mostly because most emerging markets have a restriction on the capital outflow.

Earlier companies like MoneyGram, WesternUnion and the likes were able to score sending money permission from the central banks. Nothing stops these companies from doing the same. The problem is, the outflows are limited as to how much money you can send outside the country in a given year, the margins are mostly controlled by the banks and most central banks would not allow netting-off to the new MTOs, thus further reducing their profits.

As if that wasn’t enough, they also need to register now as a local money transfer operator / licensed money exchange to do so. Somewhere along the line, the bean-counter in these new MTOs decides, it is not worth the effort / hassle / risk.