This is a quid pro quo bonus; scratch my back I scratch yours. Players receive this after putting some money in their account. The more the money deposited, the higher the bonus. At the end of the day, therefore, the player is the winner because they get to play with more than their capital investment.
Kenya is an African country and has an incredibly interesting history dating all the way back to the prehistory. Gambling was made legal in Kenya over 50 years ago and has been legal since. The country holds the monopoly over online gambling, and citizens aren't allowed to gamble on foreign websites.