I have often wondered about that, Stan. For one thing, Africans seem resistant to heat - one often sees businessmen in three-piece wool suits in hot weather which has me wilting (I couldn't survive in your part of the world). I think it is also a fashion statement - one is more likely to see a poor or rural African in shorts than an urban middle class person, who is more attuned to social expectations. And in the case of someone employed by a safari company, the boss might require his guys to wear a uniform.