It’s amazing that people who can’t manage to keep their house plants alive think that farming is technologically trivial. Gardening isn’t that hard but unless you’ve actually farmed some real acreage, involving a plow and doing a real harvest, it’s not something one just inherently knows how to do.
Thats the heart of it. There are significant steps between tending seeds, to that of feeding a population. And the game systems are not reflections of real world systems. They've been abstracted. I've read a couple posts recently, talking of cropping the early techs. I'm for an option for advanced start. But for my own games, I want to start basic tech. And would like to have our choices in early tech expanded. Want more decisions over What to tech, When and Why. With late game consequences and capitalizations based on early tech decisions.
The way I think of Techs in 4x TBS like Civ4 and E:FE is...
It takes time for a society to make significant use of something new. I imagine the time spent on tech trees, as being the time it takes to make the transition to something new. So the tech Spud Farming..
+10 Food per Grain (+20 with Crop Rotation tech)
Allows resource Vodka with Spirits tech and Distillery building
Takes my faction 12 turns to learn. 12 turns to have fully incorporated a new technology into their society. So by the 12th turn, when I "learn the tech".. A potato suitable for large scale agriculture has been breed. Sufficient sized seed stock awaits large scale planting. Fields are prepped, irrigation is in. Support industries such as Livery, Blacksmith, Seed and Feed, Hardware, etc have all scaled up to service the increased demands.
The game systems abstract and stretch real world systems out of the realm of comparison. They add feature to gameplay. Never intended as real'ish world simulation. So questions like "why must my band of survivors learn Agriculture if people before the fall already knew it", take some imagination to answer. Just as it took imagination to ponder such a question in the first place.
It would be odd to think of learning a tech to be like "BAM! There it is!". Your scholars have learned something new. Now our crops are suddenly more nutritious, our farmers more industrious. Happy day. Bless the scholars who bring instant progress. Nah. Society doesn't immediately reap the full benefit. There are things to do. Learning a tech is about that stuff occurring. The Sov chooses a tech direction, the nation develops accordingly.
Purpose of Tech in 4x TBS:
Provides players with choices, results, consequences.
Provides vehicle for player to steer a nations development.
Decisions like Guns or Butter, Grain or Metals. Magic or Might.
Provides play style options: warmonger, builder, techie, diplomat, mage, merchant etc