During the early years of the electric utility industry it was soon discovered that distribution transformers were contributing to significant line (and revenue) losses. In those poineer days it was commonplace to install a single distribution transformer for only one or two customers, like what you see here. The transformer core losses quickly added up. By around 1910 larger transformers were built by manufacturers that provided more load so that far fewer of them were needed. This led to savings to the utilities and customers with much better voltage stabilization and power reliability.

Note the unusually shaped dark-colored pintype insulator on the right side of this pole. Perhaps it is a porcelain "hat" type?