Um, akshually, I do know about this. I've launched balloons to 100,000', and part of the proper procedure for doing this is to notify ATC. Depending on the type of balloon and equipment, you might have to contact them multiple times during the course of the balloon's flight. At a minimum, it is at launch and once you have it on the ground again. I had to notify when our balloon was above controlled air space on ascent, and then again when it was descending and ETA on re-entering controlled air space. We were near an air force base, and ATC relayed our reports to them as well
Okay, but we're talking about flying airplanes. Literally everyone who has ever even remotely looked into flying airplanes in America will know that ATC asking you to copy down a number means "you messed up big time and are going to get lectured, chewed out, or worse".