People can grow vegetables and simply eat. But bread is way too complicated.
There is a bakers’ dozen of big steps to go from wheat into bread. And multiple special structures needed too.
Same with beer. Wine makes total sense but how do you even invent ale? How are these common foods everyone knows and uses?
I was thinking “imagine if mediveal people knew how to boil seawater and sell salt” and now I spent 20 extra minutes in the shower.
Beer and bread share a common ancestor: gruel. Put grain in water to soften. Works better if you also heat the mixture. Now you have a carb-rich slurry or paste in which bacteria have been killed off, suitable for staying alive.
Don’t eat it all right away. Let it sit around for a bit, and wild yeasts will grow in it first, before bacteria start colonizing it.
Pour off the liquid: that’s a primitive beer. Let the remaining mash dry out a bit; that’s a primitive bread.
Actual beer and actual bread are just evolutions along the same lines.