It's just that in those countries the people are used to blindly obeying authority, and uniform=authority. So it lubricates the process, so to speak.
That's interesting, when I used to travel in India (going back a couple of decades) I found the opposite. India is also highly structured in terms of authority, but they also tended to be very jobs-worth, doing things by the book. Trying to show authority got you no where. But putting on your best English accent, always being polite and respectful, and addressing everyone in authority at "Sir", and they melted. Doors opened, and I got access to places only maharajahs could normally see, places on fully booked flights that also had a waiting list of 50, places in the directors' car on trains... And I watched people showing authority saying "Do you know who I am?" getting refused everything.
Presumably Africa isn't the same!
PS -
Everybody I know who actually flies down to Africa regularly nowadays (probably nobody who has posted so far) says that a pilot uniform works wonders.
IO, are you speaking from personal experience here? I'm not doubting you, but some of the posts here (from any point of view) seem to be mainly anecdotal and second-hand accounts.