"All sixteen workers who had participated in the program said delivery of five packages would generally take them more than two hours to complete. If a worker drove 10 miles to drop five packages, that would earn them $15.40 in compensation per package and fuel, before overtime pay."

They clearly just dont have the density of orders for this to work. Theres videos on youtube of the amazon flex app, a 2 hour shift with a car full of boxes is mostly within a couple of blocks.