Yes, I can see that for MAD classes in particular, a human who can get +1 in three or four stats might be preferable to another race that gets +2 in one stat and possibly +1 in another. Yes, half elves can also get bonuses to three stats but one of them has to be charisma which isn’t useful for monks or melee rangers, say.
As I think folk have said, the racial ability bonuses aren’t so great as to make any race/class combo impossible, but I think there are classes for which a human is at least amongst the races with most natural fit, despite the fact they sacrifice specialism for versatility.
Which isn’t to say I’d object to Variant Humans being added, just that even if they aren’t then I’ll still probably pick Humans for a couple of my characters.
