1. Everyone gets equal service, as opposed to the people getting on at the first few stations getting a more comfortable seated ride.
2. Not new. From a Seashore Trolley Museum tour guide (yours truly), "... This car is from Budapest Hungary. As you can see there are very few seats, they being just at the very front and very rear. Trolley car companies found that they could cram many more passengers in each car with people standing. ... (then off topic) ... The car has an unusually low floor by standards back then. It ran in a subway with a low ceiling clearance so it had to be constructed lower to the ground. The low floor concept is regaining popularity nowadays to better accommodate strollers and wheelchairs." (By the way, a seatless or nearly seatless car can better accommodate an assortment of wheelchairs, strollers, and luggage.) Does Illinois Rail Museum have a comparably seatless car on display? By comparably I mean not stripped of seats after its service life was over and a new life perhaps as a chicken coop about to begin.
3. With trackwork on the north side forcing a reduction in the number of trains, the seatless concept may help a lot. How many people would prefer taking substitute buses instead?
4. I would guess that infirm persons would prefer that the seatless cars not be contiguous, although switching the seatless cars out of the trains during off hours would be easier if they were contiguous.