https://www.quora.com/Why-are-the-Gulf-countries-the-UAE-Qatar-Kuwait-Bahrain-Saudi-Arabia-not-considered-developed-countries-despite-having-very-high-GDP-per-capita-and-high-standards-of-living-Is-it-because-of-being-Muslim-majority has two quasi-expert answer
— These countries are all oil based economies, and they produce little else. Most work is performed by foreigners, and the locals just live off oil income from the government.
— Basically, there is nothing of value produced in the Gulf, from a industrial or technological point of view. There are no autos mass produced in the Gulf. No semiconductors. No steel produced in the Gulf… And that is the primary way that technologists assess how mature a society is. If you produce things of value, then your society is probably industrialized.
But the Gulf has a terrible problem with just having countries that are just hot, sandy, parched deserts, with 50C heat in the summer, very limited fresh water (Saudi Arabia actually has no rivers, at all, in the entire country!), and a terrible scarcity of raw metals in the ground.
The Gulf doesn’t produce anything because – simply put – it is usually far cheaper to ship it in from another region, than to build a factory in the Gulf to produce it. As a result, it is very hard to call the population developed.