Because they have nothing to gain and can only lose political office if they legalize it.
My thoughts on it have changed. I used to have a liberal view but I am quite against drugs now. Cannabis kills people's ambitions, most daily smokers never reach anywhere near their life's potential. I know some may disagree with me but for those who do, please respect my opinion, you don't have to agree with it. And this is from someone who has smoked a lot in my life and met many others!
I also think if it was legalized in the UK it would be widely abused, unlike here in NL where it is quite taboo among Dutch people. In UK, its not taboo even though its illegal!
RE: Why do governments hate Cannabis?