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.
People needed beer because the water was not always safe to drink. The alcohol in beer kills parasites and bacteria that might make you sick. Even kids drank light beer in medieval times for this reason.
I believe that the the claim that medieval people needed to drink beer because water wasn’t safe to drink is a bit of a myth. They built aquaducts, dug wells, etc.
As far as I understand it, it was more to do with preference (beer is great!) and calories. Beer was a good way to turn grains into easily quaffed liquid meals.
To be fair, wells and aquaducts are fairly clean ways to get water (read: animals haven’t shit or died in it yet). Rivers and other surface water were as bad as today, if not worse because it was a de facto village sewage system. Water quality issues were also mitigated by a diet very heavy in stews and soups, so less extra hydration was needed.