As a layman: It cannot be the case that most plant seeds need to be drilled because so many of their natural distribution techniques wouldn't be effective.
Most farmed species cannot compete in a natural environment.
Wild corn was a very different plant.
Need as in the farmer buying seed doesnt want to be feeding birds and mice. Drilling means a much greater number of seeds survive.
Well, corn requires drilling, and corn is king. A third of all planted ground.