Plus they have no moat. If Amazon decided to compete in that space, they could have a service up and running in less than a year that would destroy Blue Apron and similar companies.
Amazon is a logistics company that nails delivery in volumes Blue Apron cannot even fathom and Whole Foods adds pipelines for ingredient acquisition and physical locations in exactly the places where Blue Apron clients live.
All the "hard" infrastructure is in place, the last thing left for amazon is to create the app/website and market it.