Lionel 520: Why is there a cable reel on the sides?

I have done my best to take detailed photos of all pieces. All parts are in as is condition and have not been tested any further than this. The 520

LIONEL Postwar Train LOT with 520 BOXCAB ELECTRIC MOTORIZED UNIT and Transformer

Auction Database 0206 IN - Stout Auctions

Life Support Lionel 520

Life Support Lionel 520

M18 FUEL 1 D-Handle Ext. Anvil High Torque Impact Wrench w/ ONE

April 2023 Lloyd Ralston Gallery

Life Support Lionel 520

Buy the Lionel 6-18302 O Scale Great Northern Fallen Flags Ep-5

Dual Lionel 520 Boxcabs with Add-ons