There was a time when only a few famous casinos existed worldwide: Monte Carlo in Europe, Macau in Asia, and Las Vegas, NV and Atlantic City, NJ in North America.
Today there seem to be casinos almost everywhere, but not in Japan. The Diamond Princess, like most large cruise liners, has a casino, but cruise ship casinos operate only when the ship is at sea in international waters. (BEWARE: the regulator for cruise ship casinos is the cruise ship owner…)
Starting in the 1980s the USA and Canada opened the throttle on building casinos: Native American casinos on tribal land (in 1986 the U.S. Congress passed IGRA, the Indian Gaming Regulations Act); the revival of Riverboat casinos on rivers, especially the Mississippi River; more casinos on the Boardwalk in Atlantic City; many more huge casinos in Las Vegas and the rest of Nevada; and more casinos in new venues (additional U.S. States, and Canadian Prefectures such as British Columbia).
In Japan the National Police Agency serves as regulator for Pachinko Parlors and slot machine operators. There is a basic set of laws and regulations now, but they would probably need to be upgraded and strengthened to be sufficient for international-style casinos.
Tokyo is one of the great international cities of the world; folks from Osaka would argue “us too”. Both Singapore and Manila could be models for Japan to examine should it proceed with “casinos for Japan”.
Economic effects of casinos are usually positive. Social effects may be negative if the gaming is not sufficiently regulated and managed. The University of Nevada-Las Vegas (UNLV) runs a very serious and successful program for gaming, aimed especially at chronic gambling (a very bad habit). On the other hand, my wife and our daughter enjoyed dinner at a casino and a few hours on the gaming floor (mainly slot machines) together for many years.