It may not be beneficial for a government to ban a vice as the costs of banning it may cost more than the costs of society to bear the burden of dealing with the vice.
Of course, there are separate discussions as to how governments should allow capitalism to interact with vices. Take tobacco as an example, a generation ago, tobacco was allowed to be advertised as any other commercial product. That has significantly changed since then, to the point where some governments go so far as regulating packaging.
I expect gambling is on the deregulation path as it is a way for some governments to raise revenue without raising common taxes while the societal costs are seen as low.