That's another story, why would someone ask for foreign investors when they can make easy money with their operation, gambling does not require a lot of capital to start, and it's very lucrative business especially if your government is supportive in gambling platform so getting investors is not a wise idea.
If a country's gambling industry has the potential to compete on a global scale, then there will be many potential foreign investors who want to invest in it, and I think the government has no reason to reject it. In general, if foreign investment in a country increases, then the country's foreign exchange reserves will also increase (especially for developing countries) and of course, this is a benefit for the government.
I guess what you are talking here is a land based casinos like Las Vegas or the Macau casino, well, I guess if that's what you think then I think it really needs a foreign investors as developing countries does not have the capital to compete with the best casinos in the world.