gambling is often seen as a harmful habit. my question to you is, in a completely free society, should someone be prevented from providing gambling services for the good of society?
As long as the law does not prohibit that person or company from providing grabbling services, they shouldn't be prevented because gambling is a business venture too.
from an individual point of view, it is everyone's choice to gamble or not to gamble. the management of your money is entirely up to you in a physical sense. but that doesn't change the fact that some people are going to go bankrupt, their lives are going to be very difficult with the existence of gambling. if it was up to you to allow gambling, knowing that it is inevitable when enough people are involved in gambling, would you consider it ethical?
From my point of view, gambling is ethical if approached from the yardstick of fun, but when seen as a source of livelihood or you gamble with amounts you're not prepared to lose, it turns unethical.