MY COMMENTARY:
Walmart and Best Buy are in the business of buying and distributing products to many shoppers, not buying products from a few shoppers for resale. The former depends on a massive and consistent supply of goods and a mass buying discipline. The latter is fundamentally a customer service with no supply chain consistency.
Then there's the matter of delivering this service using an in-store kiosk. Even under the best of circumstances, the number of potential daily users is limited by simple physics: one user at a time per machine; so many minutes per user. You can do the math--the productivity is limited. It's just a poor fit for mass retailers like these.