I don't understand why BTC should be a store of value

BTC cannot and should not become a store of value for the world, because BTC can't possibly scale without resorting to the centralized Lightning network which defeats the whole purpose of a peer-to-peer cash system. Look at El Salvador's Chivo experiment. It was a complete failure where most people didn't use BTC even though the government gave them free money and free app to use it.

The centralized solution known as Lightning doesn't work and shouldn't work if you are for decentralization where regular people rule, not the people who own the Lightning network.

Another reason is that the more users BTC has, the slower and more inefficient it becomes. This kind of technology can't possibly survive in the future where more users would mean worse user experience. For example, if YouTube or Twitter slows down every time it gains new users, all the users would leave for a better, faster product.

Also, the vast majority of the world population does not think that BTC is a store of value. It's the opposite of gold which is universally recognized as a store of value for thousands of years. Unlike BTC, the number of users don't affect the nature of gold at all.

Just because Michael Saylor says BTC is a world store of value, doesn't make it come true. In order to become a SoV of the world, it needs to be functional and not inefficient with a growing number of users. BTC won't be functional if it has billions of users even with Lightning. Its small block size make it impossible to scale, which means that it's not for the billions of users around the world. If it has to resort to the centralized solution like Lightning, BTC is just another tool of the government to control its general population.