Serious question - why did it go grade based? Who is the influential family?
That is a good question. I have wondered where the concept came from, how was it developed.
I would be surprised if they gave up the name of the influential family.
I believe it was, in part, to make it easier for college (or HS) coaches to know what they are looking at. When looking at a U-13-U15-U17 they would not know exactly what year the kid was graduating, when looking at 2018, they know.
I don't think anyone envisioned opportunistic people exploiting this the way they have, but here we are.