Kenya central banking history by: Arjen (webmaster)
I'm not a specialist in Kenyan banking history - not even close ;-) - but I guess the reason is the same as everywhere else:
Every national government wants to have it's own currency and it's own central bank to be able to control their own financial and economic future, control the volume of money, set interest rates, etc. By manipulating these parameters they hope to keep inflation low and to stimulate the economy.
This is changing, however. It's claimed that the European Union is more or less the first example in history where nation states do not have their own currency anymore. (The EU is a politcal body, it even has some features of a state, but it clearly isn't a nation state.)