It's an interesting thought but let me tell you it's all about perspective
Does stealing a good thing? No, but why in the story of Robin Hood, he is consider as a good guy although he is a thief?
Are drugs a good thing? No, but when its being used for relief patient's pain it become a good things
Why gambling consider as bad things? Because there are people steal for gambling, bet his fortune in gambling table, even sell his home to gamble and that is a bad and irresponsible gambler
If today all of the gamblers become a good gambler, never harm anyone, used conscious mind when they bet, the society will never labelled gambling as a bad thing, gambling is just a game, a game for fun, its almost the same with playing arcade game, where you need to spend a coin to play