Wanting to know your NSS throughout..isn't that just one more thing that's going to be on your mind that shouldn't when you're flying/studying? .... It's a good confidence boost for someone doing well, but if a guy finds out he's at the bottom of the pile NSS-wise, maybe it would be a detriment when he should be working harder to fix what's going wrong. IMO. But then again, this just might be one of those "when you get to primary, you'll understand" things.
I understand what you are getting at, but I still think it's important to be able to see how you are doing. It's not the guys at the top who benefit from being able to get an accurate gauge on their performance, it's the one's on the bottom. Case in point.
A buddy of mine went to the KLRU det and did just fine. During that time he never had a jacket review or anything of the like because we were on det. He never got a pink sheet and never had a grade sheet that said he was struggling. In fact most said something along the lines of, "good progress, motivated student." He got back and found out that you could check your NSS at stucon. Sweet; he was in the mid 50's. He started RIs and was doing okay. At a jacket review his flight leader asked him how he was doing. He told him RIs are tough, but he was coping with the double pumps alright, and hey, no worries, he had a 50-something NSS going in. All he wanted were helos so he was money. The flight leader became concerned because you typically lost 15 to 20 points off the NSS that they project before RI's in our particular squadron (this is a time and place thing, don't try to apply it to your squadron at your time and then get pissed when the number doesn't work). My buddy was told that he might have to go to a board in order to select because his NSS would likely be in the 30's. They put him on SMS, stopped double pumping him, and he studied his ass off and squeaked through. He was a good dude, and like many suggested, he never worried about grades and just tried to do well on every flight. No one ever told him he was struggling. Had he known how marginal he was doing he could have requested SMS and gotten more help from the command earlier on and it wouldn't have been as close as it was. Knowing where you are is important, but stressing about what you have already done is a waste of time.