The story that I heard is that shisha was banned because Uhuru's son was at a shisha lounge and his shisha was spiked with cocaine or something. I don't believe the story since you can't smoke cocaine unless its turned into crack and crack isn't something that people use here in Kenya. I think its because the big tobacco companies couldnt' control the shisha market and the petitioned the government to protect their monopoly on tobacco products. But you can still very easily find shisha lounges, although they are occasionally raided by the police. As for why khat can't be banned, that's because khat is a big part of the economy of the Meru and Embu regions, and its part of the culture of certain communities like the Somalis, Arabs, Indians, Embus and Merus. Banning khat would just piss off the people who depend on its cultivation for their livelyhoods and the people who see it as part of their culture.