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. They do not have the capacity to provide full, rated service to all users simultaneously.

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.