You're completely missing my point. Without any external pressure, multiple peoples concluded that settling and eating grass was preferable to being nomads. Yes, this includes the ancestors of the bison hunting plains tribes. It was only with the population collapse due to smallpox and introduction of horses where the nomadic way of life became dominant again.
Until the invention of firearms, nomads had equal footing with settled people, if not an advantage (e.g. Attila the Hun, Genghis Khan). The main advantage that agricultural civilizations had was population size.
"Without any external pressure, multiple peoples concluded that settling and eating grass was preferable to being nomads."
Portraying it as an individual choice is inaccurate. The process of populations becoming sedentary(and agrarian) spans over multiple generations and wasn't really reversible. The early settlements likely only worked because they had some method to force people from leaving and the later settlements had to be sedentary because their neighbours were sedentary, it had a cascade effect. Oversimplified but that's the gist.
"The main advantage that agricultural civilizations had was population size."
Metallurgy?
Not just firearms.
Stone axe vs bronze sword?
Bronze sword vs iron sword?
Iron sword vs steel?
Nomadic people got their advanced weapons usually through trade from settled ones. The nomadic horse archers dominance was rather an exception, also their kingdom included cities where the weapons they used were made.
"Without any external pressure, multiple peoples concluded that settling and eating grass was preferable to being nomads"
And there always was external pressure. Also .. our knowledge of that time is just fragmentary. We don't even know the real names of those cultures.
So yes, clearly there were benefits to settling and planting corn, otherwise humans would not have done it. But to my knowledge, it is not correct to call it a voluntarily process in general. Once there are fences, the nomadic lifestyle does not work anymore. Adopt or die out was (and is) the choice.