Schwinn with Plastic Soap Jug

This is a great old bike and a great mystery--at least to me. Ok, forgive my possible ignorance, but what the heck does the blue plastic soap jug offer the typical cyclist? In terms of just style, the blue jug is strangely appealing. Perhaps someone on the Internet can offer a hint as to practical value, or I'll just ask the person who rides this Schwinn next time I see him or her at the bike rack.

University of Illinois

best

Robert