That most banks and supermarkets don't have toilets for clients was not a pressing issue back in the day when Nairobi was cleaned at night.
See, the then City Council of Nairobi had public toilets galore in every estate, the city centre including slums. The Kanjo cleaner often arrived in the morning and cleaned the previous day's mess as the toilets also had a public water point where the precious commodity was sold for Sh5 for a 20-litre mtungi.