And they'll have fun carrying around rivetted boxes, no nesting boxes to save space..
If two 130 lb robots going at full speed hit the same box at the same time at the top of the ramp, something's gotta lose.. and the most likely candidate for that is the bin. Just like the reason you can't have protruding stuff in teh wire mesh. If two robots get in a fight with both robots' wheels meshed in, the wire's gonna lose.