Day-treks, safaris, and city exploring in Africa can require long times away from a place to use the bathroom.
Not every place you stop and shop is going to have a place for you to go, and if you are out on safari, not every place is exactly safe to stop and get out of the vehicle (you don’t want to end up as an animal’s lunch).
What’s worse, you’ll probably end up going to some tourist spot sometime along the way with a long restroom wait, and that of course is no way to spend your vacation.
So even if you don’t have to go… you can at least try. If there is a restroom available, go use it — you don’t know when you’ll find one again.