It’s a story I know
By 2021, the NFL had a restriction on the back number by position.
This was introduced in 1973 to clarify the distinction of positions when the TV was reduced.
It was a strong regulation that could be almost absolute before the 2000s.
Until recently, it has been hardened with quite old traditions.
(This limit has been greatly released in 2021, now that OL is not except 50 ~ 79.)
To roughly distinguish,
(The position image that comes to mind when you look at the back number instead of the exact distinction)
1~9: K, P
10~19 : QB
20 ~ 49: RB, CB, S (preferred 20,30, 40)
50~59 : C, LB
60~69 : G
70~79 : OT
80 ~ 89: WR, te
90 ~ 99: DT, the
So I might think that there are few number of stars in the NFL before the 2010s
That is because the number of digits was traditionally considered the number of K and P.
As a side note, there was no such restriction from the beginning. It meant to respect student freedom.