Like the other reply says, it's probably just the farmers don't have time or don't want to.

I expect you could make the same comment about just about everything on the planet that is grown or made, but then sold by someone else. The original person could try to sell it to consumers, but that would take so much time and effort they wouldn't have time to grow/make the thing in the first place!

Peter here (author).. They didn't have a need, desire, or employee to run that type of operation. The farm didn't have a website when we started, so my sales pitch to them at the start was 'Even if we miserably fail in this project, at least you'll get a free website out of it'..

I think it's less about tech-savvy and more about deciding to go larger-scale and adopt all the problems that come with that. Handling order fulfillment and customer service isn't something most farmers probably want to do.