Gambling is a real danger and mindfully,no religious organization would like to promote it because it's sinfull and harmful according to scriptural references/examples.Whether Religious leaders should carry out responsibilities about social policy and regulations varies depending on the nature and government of the country.
Gambling is harmful for gamblers that don't engage in it responsibly but I don't see it as sinful and I don't know where Christian religion specifically said that it's a sin. Morally some people condemn gambling because of it's negative effect on gamblers, people don't take notice of responsible gamblers because they don't show any signs of addiction. I don't know when the pessimism about gambling will stop, as long as irresponsible gamblers will continue to show traits of addiction people will continue to see it as something sinful and harmful.