Another continent that is slowly ditching human personalities from its coins is Africa. After World War 2 decolonisation gathered pace, and by 1980 it had mostly been completed. It was of course important for the newly independent countries to honour their founding fathers, so portraits of Nkrumah (Ghana), Kaunda (Zambia), Kenyatta (Kenya) and Nyerere (Tanzania) were all to be found on circulating coins, both during their presidencies and after. Tanzania’s coins still carry Nyerere’s portrait, but coats of arms have replaced presidential portraits on the circulation coins of Ghana, Gambia, Malawi and Zambia, and Kenya is planning to follow suit. Though it is generally the rule that reigning monarchs, in contrast to presidents, always appear on their national coinage (not just in Africa but worldwide), it is interesting to note that, unlike his father (or Mswati III, reigning king of Swaziland), Letsie III of Lesotho has never had his portrait depicted on the coinage.
The USA, by contrast, has long had a tradition of honouring its former presidents (though never a current president, of course) on its coinage and, since it is such a conservative country, that is unlikely to change any time soon, so the trend will never be universal. I am talking here only about standard circulation coins of the world: human personalities, of past and present, will always be in demand on commemorative circulation coins.