I believe it's a combination of a lack of customers and lack of infrastructure. It's a big continent to cover with the necessary fibre capacity, and the market is much smaller for nearby services.
Also what you don't see in things like this, or even a list of datacenter locations, is the relative sizes of the datacenters. After US east/west coasts and Europe, datacenter capacity rapidly tails off. Parts of Asia have plenty but not on the same scale I believe (although I don't know about the Chinese market). The difference in size can be quite a few orders of magnitude between different regions.
Also what you don't see in things like this, or even a list of datacenter locations, is the relative sizes of the datacenters. After US east/west coasts and Europe, datacenter capacity rapidly tails off. Parts of Asia have plenty but not on the same scale I believe (although I don't know about the Chinese market). The difference in size can be quite a few orders of magnitude between different regions.