It's simple right, we plant a seed, nature grows the seed, we eat the seed.
How farming works (simplified version):
That's a fine plan unless we want to grow food more densely than nature typically allows, or in a season when nature isn't so friendly. Or if we want to grow crops that can't be naturally grown in our specific location because it's too hot, too cold, not enough rain, too much rain etc.
We can use technology to create ideal environments for growing crops. We can provide just the right amount and color of light and the perfect amount of water and nutrients. We can stack hydroponic platforms vertically in order to exponentially increase the amount of food we can grow in a square foot. We can use technology to create environments that allow us to produce food year-round.