It is said that this is because, although the Tokyo-side departure station on the Shinkansen line is located in the city center, those of Tobu are located on the eastern part of the city (the so-called shitamachi area), such as Asakusa and Kita-Senju.
東京側の発着地が都心にある新幹線と異なり、東武は浅草・北千住という東側に偏った位置（下町）にあることなどが主因とされる。