[MrForbes]

Look at it this way....it takes a lot of work to lift a 130 lb robot twelve inches, or even four inches. The lifting mechanism would have to be powerful, the structure would have to be strong, and also compensate for the balance problem (lifting one robot next to another one will cause the lifting robot to tip, unless it has some type of outrigger to stabilize it). Since all the robots already have a relatively powerful drive system, why not take advantage of it, and let the other robot drive up yours, using the other one's already available power system? Deploying a ramp takes little work.

I'd be really surprised to see more than a handful of robots that try to lift another one.