[notanzaiiswear]

It surely is already very expensive to leave an apartment empty as it is. There also seem to be special circumstances and laws in London.

But lets assume the worst, that it is all just pure evil capitalist speculation: even that is not necessarily bad. They try to anticipate future demand. So they anticipate that in the (near) future, somebody will need that apartment even more urgently than the people looking for housing right now. So it is better to keep it available for those people in the future. Think about keeping ICU units ready for future Covid patients for an analogy.

So what if the speculators are right, and the future buyers really have a higher need than the current ones?

Also I think if there really is just speculation, especially foreign investors, why not build cheap houses and sell them to the speculators for a lot of money? Nobody will ever live there (according to the anti-capitalists), anyway. Seems like a good way to make money for a country.