The City of London is notable for allowing businesses to vote because so few people live there. There is one residential district inside the City in the Barbican estate, the rest is commercial.
The local population number have absolutely nothing to do with the existence of corporate votes in The City of London. It's not even the smallest local authority by population, the Isles of Scilly are, and corporations have no votes there.
Given its small area, I doubt anybody would ever be interested enough in fighting with The City to revoke its ancient rights, and independence from the broader UK government. Past monarchs and leaders have attempted to strip The City of its rights, all of them ultimately decided it wasn’t worth it.