What a waste of time, police is for crime not personal choices. The government could be taxing the lottery while helping to ensure its run properly, instead they are wasting the countrys money chasing their own tails for no possible benefit. Double negative, this is what makes a country poor because people will gamble on something or other anyway. How would they view marbles for money 
Even a simple crime like stealing is not assured by the police, much more if it was gambling. Not to mention if it really is banned in a certain country, I bet (no pun intended) there are a lot of corrupt officials that let these underground casinos operate--they bribe them in exchange for protection. It is indeed a waste of money, not a very wise decision. A bit unrelated but in the US, they even legalized weed, I don't have any "statistical" information to present but we know pretty well how it could affect the country--economic-wise that is.
I think you misunderstood what @STT has said, he didn't mean those police bribing gambling games to protect them in exchange, though there are something like but only for illegal gambling, just like what you have said, but @STT were trying to say is that the Government gives permit to certain gambling games like lottery and casinos, that is why police are in charge just in case if there will be crimes about gambling, since policemen are under of the Government's hands.