KUWAIT CITY—The persistent slump in oil prices, combined with rapid population growth, has forced all the Gulf monarchies to consider austerity and economic overhauls. The reaction here in Kuwait, by far the most open Gulf state, shows just how hard these measures could be to implement—and how much opposition they are likely to attract.

Ever since oil started to flow nearly a century ago, most of these monarchies were based on a clear social compact. The ruling families, be it in Saudi Arabia, Kuwait, the United Arab Emirates...