The second point described by the OP also seems to me the most reasonable. Large salaries and desire, as well as opportunities to get some sensations, make people look for ways to have different kinds of entertainment. For those who can afford to spend the amount that for another person from a poor country may be important for their life, entertainment does not end with going to a restaurant or a trip to a resort. People have seen a lot in life; they feel satiated, so gambling attracts them with its unexpectedness. And of course, the fact that the government in no way prohibits, but on the contrary, forces people to play, placing colorful advertising, is also a good motivator for passion for gambling.