I would also like to add that although NORAD tracks all of these satellites and debris, they might not actually know which is what (particularly after separation of payloads from the launch vehicle).
Publishing TLEs for these unknown objects is particularly helpful to ground stations, allowing them to plan their scheduling while attempting to contact and identify newly launched satellites.
Take, for instance, this screen shot below from AGI's Systems Toolkit (STK) software that NASA IV&V engineers were using to help locate their newly launched cubesat STF-1 (which was among 12 other cubesats on the ELaNa XIX Launch).
Basically they picked an unknown object's TLE, tried to talk to it, and if it didn't answer they picked another one on the next go around. Once you find yours, you can essentially 'claim' it via Space-Track.org and submit the identification of the object.