That probably the depends on the country and the specific taxations laws which are applied to casinos and betting houses, to be honest. Though, if we are talking about countries like the United States, then there is no doubt the IRS (the agency in charge of collecting those taxes) get a lot of money from the casino owners and also from the people who happen to hit a jackpot or win the lottery.
Ironically, in the USA there is also a way for people to declare their losses due to gambling and get a discount on the money they need to give to the IRS.

Though, it must be clear: The government itself is not behind the increasing growth of the gambling industry. It is about private companies wanting to capitalize on the edge of the house and the huge volume of people willing to risk money.

By the way, the amount of gambling addicts currently struggling to their urges of gambling should not be underestimated, there are probably thousands of hundreds of people who are addicted to gambling and they have not realized yet.