Why didn't Saudi Arabia join the United Arab Emirates?

The reasons why the country does not join the UAE are as follows:

Saudi Arabia and UAE have different ideas and interests in politics. Saudi Arabia is an independent kingdom with its own national system and government. In contrast, the political system of the United Arab Emirates is more complicated and requires coordination and cooperation among the seven Emirates. The Kingdom of Saudi Arabia may think that joining the UAE may weaken its independence and national interests.

There are also economic differences between Saudi Arabia and UAE. Saudi Arabia is the largest oil exporter in the world, and its economy mainly depends on the oil industry. UAE is a diversified economy, not only relying on oil, but also developing industries such as finance, tourism and real estate. The Kingdom of Saudi Arabia may think that joining the United Arab Emirates may limit its autonomy in the oil industry, and Saudi Arabia's economy is large and powerful enough to develop independently.