This was to ensure stable supply destinations of electricity, and it was a common practice for many companies such as Tokyo Dento (which established the subsequent Enoshima Electric Railway and Tobu Ikaho Permanent Way) before World War II.
これは安定した電力の供給先を確保するのが目的で、戦前は東京電燈（後の江ノ島電鉄線や東武伊香保軌道線などが該当）など多くの会社で行われていた。