I don't know, but it might have been to prevent kids/teens from hanging out in there. I once went in there and there were a bunch of kids camped out, laying ont he floor, their wet clothes draped over the rails in the center. All they were missing was a pot of hobo chilli hanging over a campfire! We made up a story about the "Vagabond Children of Main Street, USA" as we could only assume they were running some kind of Oliver Twist style pickpocket ring.
Seriously, sometimes the "
Disneyland People" have a tendency to think they own the place. The benches may have been removed to deter loitering. I think they ahd converted it into a shop briefly too and they may have just never put them back.