I did wonder that for a second. I really hope OP isn’t wondering why there are no Premier League top scorers from before 1992.

Check the list of top scorers in the English top flight here: https://en.m.wikipedia.org/wiki/List_of_English_football_first_tier_top_scorers

Out of the top 50, I get 8 predominantly in your new era and a similar number in the 60 to 90 ish bracket (expanded a bit to make a similar time period).