DND_Reborn
The High Aldwin
I’m OK with humanoids not following the same rules as monsters. Why? Because those are the monsters’ only weapons. They use them and have evolved to use them as their primary forms of attack and defense.
Most humanoids do not. We use weapons. Unless you’re extensively trained to use your feet or fists in combat, you just flail around like a wild idiot. And what do we call people in D&D who are extensively trained in unarmed combat? Monks. And do monks basically get finesse with their unarmed strikes? Sure do.
In comparing unarmed strikes by humanoids to natural weapons, I completely agree that without some training it makes sense for humanoids to defeault to STR only. But, the problem is, people are proficient in unarmed strikes now. It wasn't always the case until the new printings, as unarmed strikes used to be considered simple weapons (and most notably sorcerers and wizards were not proficient then). I think the designers went too far in the changes, personally.
Keeping proficiency in unarmed strikes its own "thing" would mean certain classes would start with it, others might get it as part of a subclass, and others might pick it up through a feat such as tavern brawler, etc. or multiclassing.