im not sure im all that surprised that more people didn't notice him. there are plenty of musicians (granted not always of that caliber) that play in Grand Central and Times Square. And while I may 'notice' them, I'm usually in such a hurry (read: late) that I just pretty much run on by.
If I did have the time, there are a few occasions where I'd have liked to have listened. I usually stop after work to listen to them, especially since I'm rarely in a rush to get anywhere.