The section you quoted from is from an out of date section of the old PHB labeled and you are taking it out of context.
The sentence you keep quoting does not say commoners are proficient with simple weapons, it says "most people" are and you conveniently left off the sentence proceeeding:
"Your race class or feats can grant you proficiency with weapons or certain categories of weapons"
This is the opening sentence from the paragraph you keep quoting and it makes it explicitly clear who they are talking about - "YOUR" proficiecnes, not a random NPC or commoners or anything else, they are addressing YOU.
Further if we are to say this text applies for all NPC then that means they need a race, feat or class to get proficiency because the paragraph you are qouting makes it clear that is how you get proficiencies. Not by being a commoner and since "most" people have these proficiencies then clearly some don't.
So what is the race, class or feat that gives commoners this proficiency?
It is not. It is written in 2nd person.
Your position makes absolutely no sense. You've just claimed that if there are 10 million people in the world, over 5 million of them are PCs, because that's the only way most people could be proficient with simple weapons and only be talking about PCs.
Thankfully, you're wrong with your position and the PHB 100% includes the entire game including PCs. The 5e DMG says so.
Page: "This book has two important companions: the Player's Handbook, which contains the rules your players need to create characters
and the rules you need to run the game"
Page 5: "The Player's Handbook contains the main rules you need to play the game."
Page 9: "This book, the Player 's Handbook, and the Monster Manual present the default assumptions for how the
worlds of D&D work."
The PHB contains the game rules. Not player rules. Game rules. The PHB contains default assumptions for how the worlds work. Worlds include NPCs.
Except the parts which have been replaced ... and that includes proficiencies by race (and race in general in fact) and therefore that whole paragraph considering the first sentence.
No. You are allowed to keep any old rules you wish. You aren't required by the game to update to the 5.5e versions.
Most people, even in the out of context way you are using it, means some people don't. It means exactly the opposite of what you claim - that being a person does not automatically give you proficiency.
But most have proficiency. Not the zero you are claiming.
No they are not. The entire definition of person is not even clear.
A commoner is a specific monster, and one of over 500.
So tell me then. Who outnumbers the commoners of the world? Understand that there isn't one commoner in the entire world just because they are one stat block among five hundred. There are lots and lots and lots of commoners. That's why they are called commoners and not uncommoners or rarers.
No it doesn't. It does not say commoners are proficient with anything.
Riiiiiiiight. Commoners are not among "most people."
Gladiator is already a background in the 2014 PHB - page 131. It provides an unusual weapon like a net or trident as starting gear but does NOT provide proficiency with that weapon. To emphasize my earlier point you get the weapon, you presumably use the weapon every day, but you don't get the proficiency in the weapon .... and any PC can take that background. The proficiencies you get from Gladiator are Acrobatics, Performance and a Disguise Kit.
Backgrounds are not for weapon proficiencies. They are supplemental to class which dictates PC(but not NPC) proficiencies. NPC proficiencies are from different areas of the game.
I am confident a gladiator subclass will not provide proficiency in any class of weapons. If they have proficiency it will be because of the class it is attached to.
Um. If they are a subclass of fighter, then gladiators will be able to use all weapons. They aren't going to be a subclass of whatever "class" you think gets only one weapon proficiency.
This discussions of Gladiators brings up another good point. PCs Gladiators use weapons in their performances every day, but they don't get proficiency in them .... yet commoners automatically do???
There aren't going to be many wizards, sorcerers, or druids with the gladiator background out there. Those corner cases that do, are just that, corner cases. The overwhelming majority of gladiators are going to be fighting types who have proficiency.
NPCs don't have classes and the only official Gladiator published for PCs to date did not require the Fighter class and did not provide any additional weapon proficiencies.
The 5e rules on that are still in effect, so some NPCs do in fact have class levels. It's an option for NPCs in the 5e DMG.