It doesn’t mean that there can’t be very fast growing companies in developed markets — i.e. Credit Karma in the US for example — but they are more likely to be in areas with less competition from traditional finance, in other words “different” products rather than “better” products.
Digital shifts cost structures from CAPEX to OPEX. Traditional finance is based on physical outlets, which means that growth tends to be linear rather than exponential. As the number of customers increase, fixed costs also increase in a linear way. This is of course a very rough approximation, but that’s not too inaccurate for retail banks. This is different for investment banking which doesn’t have the same CAPEX constraints, which is why investment banking and capital markets are so important for universal banks — but the total universe of clients is much smaller too.
Snapchat may be solving an important problem for well-connected young people in America who don’t have to worry about basic needs. But whether it’s unemployed young people in St. Louis looking for their next paycheck or a family in Flint, Michigan worried about clean water, many Americans have more immediate problems.