Because all land on the planet is part of a country already, with exception of Antarctica. Even on the rare occasion that new islands break the ocean's surface (the last was in the 70s) they're immediately claimed, there's 1, I forget where, that was even disputed territory. Even "private islands" are just owned land like any other owned land and are still a part of the country they territorially belong to and must abide by that country's laws. You can't just buy an island and declare it a country, and even if you could it would never be large enough to be self sustaining. Thus would require trade with other countries, and those countries could easily refuse to conduct trade with it if they don't like your "hedonistic" laws of "debauchery".