The transformer is dimensioned based on the max capacity of the houses in the neighbourhood

No, it isn’t. They use considerably smaller, cheaper transformers, based on the maximum expected load. A 500A transformer might serve ten 200A users.

Those ten users might never use more than 400A total, even though each of them might use 150A+ from time to time. It doesn’t make sense to install a 2000A transformer when it will never see more than 400A.