ummm warriors are either paid killers or people who train to kill because they decided killing people is a good way to make money, or they just like killing. Being skillful doesn't change the fact they murder people, in d&d usually for cash or loot.
I am sorry that your scope of warrior is soo ... small and thusly tied to DnD's limited interpretation and expression. I might, if possible, attempt to expand your concept of what a warrior is. I will first take MMA, and note very quickly that in counter to
warriors being only there for murder, and make the distinction that combat is not always murder.
I certainly see MMA fighters, (hrmph it's in the name) as warriors. To this end, yes they earn money for, here it is again,
combat. Instead of lethal weapons they use natural weapons, which still have the potential to kill, but that really isn't the point is it? They get in a ring and fight. Now let's put your average guy into the ring. Now according to you, no special training or moves are required by the farmer what so ever. Surely there will be no difference in skill or relative ability to defeat one another.....
And here, in a real life example, is where your argument shows its divine limitations. There is most certainly a training requirement, a unique set of skills that will allow the
MMA fighter to over come his
average guy rival. And it will happen nearly every single time. This also rings true if each combatant has a long period of time fighting in their own native fighting style. A dedicated warrior will always beat out an average person, every single time...(nearly) But as a general rule, yes.
Lastly many professions take part in combat to protect, self defend or to acquire loot. This does not make every single one of them warriors. A warrior is a specific expression of combat, not just a combatant.