"...amateur players find Black easier to play than White because they are
better prepared with Black. "
I think this is very true, it is certainly true of me and others I know.
I'd hazard a guess that there are more dedicated Black opening books
(those that cover just one specific opening) than there are White's.
Just looked through my library of junk that I have gathered over the years.
The Bishop's Opening, The Scotch, 3.Bb5 v the Sicilian (3 books).
Four Knights. Italian Game, English? (Never played 1.c4 in my entire life).
and that appears to be it.
Philidors Defence, Two Knights(2), French (2), Pirc (3) Kings Indian(4), Sicilians(4)
Latvian(4) Caro Kann, Alekhine, Benko, Petroff(2), Scandinavian(2). Elephant,
and Counter Gambits for Black v The Lopez,
Incredibly for the past 20 years as White I usually played the Lopez if I got
the chance. I do not have one book on the Lopez for the White side nor
have I read one. (after the first three moves what more is there to know?)