Many of the auto cars (and especially on the NP given the radial roof design) lost their ability to haul cars as the autos became larger and longer and the new Evan's automobile loading equipment would no longer be able to be outfitted, AND provide clearance once the car was lifted. Evan's automobile loading equipment changed and perhaps this entered the equation, the changing of Evans equipment. Clearance from the floor on up to center ceiling was paramount and the difference of height inside a car from 10 feet 2 inches to 10 feet 6 inches was worlds apart. Radial roof design while strong and robust, needed tension bars as part of the structure. Boards were weaved at angles in compression and held at tension by metal bars and that loss of a few inches, took these cars out of auto service (and eventually other railroads cars also as interior heights became too restrictive.) 
     These 5000 series still worked well enough for large for not terribly heavy bulky items ordered through your Sears catalogue, such as stoves, washers, couches, fridges, and so on. In other words, in service where they would be seen all over the US.
    For the NP, the solution regarding auto haulage was the 8000 series of cars with Murphy roofs instead of radial. 

  I'll attach a photo.   The longitudinal wood braces plus the metal cross braces took the precious few inches of roof space that made a difference. (For want of a nail the kingdom.....) 

                                                                           Paul, of the car,    very...very....nicely....done.                                                                      James Dick - Roseville, MN