According to the rules of every country, when someone crosses 18 years, he becomes an adult and then he can make any decisions he wants. So if gambling is legal in a country it is only natural that the government would demand a tax on it. If gambling is legal in your country, your government may charge a VAT that is fair and you must pay it. Since you are old enough to take responsibility for your own decisions. In this case you cannot blame the government. Because you are making your own decisions. The government will not force you if you do not gamble and neither the government nor anyone else will stop you if you gamble
I think the OP who brought about this topic is from my country. From my little knowledge, I don't think gambling is 100 percent legalized in the sight of the country's law and even if it was, there have no been any working policies set aside to regulate those law gambling. So why will taxes be imposed on people when the government in itself isn't taking that responsibility of properly regulating them.