Because there is evidence that Marxists had tried, and failed, to do what Amazon has now succeeded. Project Cybersyn comes to mind:
https://en.wikipedia.org/wiki/Project_Cybersyn
https://www.newstatesman.com/world/2018/08/project-cybersyn-...
However, what Amazon has done is just characteristic of "organized industries", which Hayek conceded in his essay, The Use of Knowledge in Society, as being a "halfway house" between Soviet-style planning and free markets.