I concur with you that economic status is not a good indicator of country's currency value. A classic example is China and Japan, among the strongest economies in the world, but surprisingly both of them have weaker currency. Unlike Kenya, these two countries prefer there currency to have less values in comparison to the dollar because it allow them to have a competitive advantage in exportation. That is the reason United States Govt has been complaining about this, and asked China to allow its currency to float.
On the other hand, I vehemently disagree with your assertion that Kenyans would prefer Kenya shilling in lieu of the mighty American dollar. American economy has been around for sometime now, and more importantly has stood the taste of time. It's no wonder the US dollar is a global currency. To make a long story short, it's only a fool who would prefer Kenya's shilling in lieu of the mighty dollar.
Last, let me ask you a simple question for the sake of this debate if you don't mind. Imagine you are a Google manager who is in charge of preparing payroll for Google's employee in Africa. You are contemplating on whether to use Rand or Kenya shilling to pay your employees, and the exchange rate is as follows:
1 $ = Rand 7.47 and 1 $ = Shilling 77.47
Which currency would you choose? Bear in mind your number one priority is to cut down Google's cost of operations.