On the upside, a highly curated allowed character race list can serve as a check dam against players whose preferences are different enough from the GM's that it would like be a problem.
GM: This is a low fantasy, mud and blood, humans only in a mythical British Isles during the Saxon Migration mercenary campaign.
Player: Can I play Gnome Illusionist Jester?
GM: Not the table for you, my man.
GM: This is a low fantasy, mud and blood, humans only in a mythical British Isles during the Saxon Migration mercenary campaign.
Player: Can I play Gnome Illusionist Jester?
GM: Not the table for you, my man.