Being a city-state and being a city in a country is ultimately different. Almost all capital/economic centers in every country is richer than other cities in the same country, because they have a concentration of economic resources which other cities don't have. You can't deny that Shenzhen's prosperity is largely because of China, just like Manhattan's prosperity is largely because of the US. They wouldn't exist without the main body. Shenzhen/Shanghai rightly pays taxes to the central, because many of the taxes (like import tax) are country-level.
Singapore spends the most on defense every year, higher than education or healthcare. Our defense spending is even higher than Indonesia and every Singapore male spend 2 years of life in the military.
You may think it's useless because in your worldview only US, Russia and China are relevant globally. But the military's relevance for Singapore, I know it's still very important.
I do know that Mahathir threatened to cut off Singapore's water in the 1990s, and only shut up when LKY threatened to invade Malaysia if he dared to do that. Now he's back and is raising the water issue again, but you can be sure that he won't dare to cut off our water.
Read more at
https://www.thestar.com.my/news/nat...t-want-military-alliances#RkAG4RT88pScHvsx.99