RW operations in climb

When I was finishing my commercial cross countries last semester, I flew into Midway a lot, and when I was on with Chicago Approach, I would sometimes have ORD tower tuned into COM2 just for the heck of it, and when the weather was clear just about every airplane that took off was told to "contact departure, speed restriction lifted go fast." I'm assuming that they were just busy and wanted the airplanes to get the heck out of the airspace, especially since it was good visibility. I heard that on more than one occasion, though, so I don't really know how common it is.