Scan and Go is a great app; I use it every time I shop. It works well in Sam's because security is a person at the exit, and customers bag their purchases. The only limitation is government not allowing self checkout on some items like liquor and tobacco.
A more complete consumer shop and pay application is Future Proof Retail, with a major focus on LP and one app works across multiple retailers.
Consumer shop and pay applications will have a high level of consumer adoption when:
Retailer modify checkout processes for this new way of shopping;
Traditional POS hardware providers, who will lose a lot of revenue, surrender to consumers.
Of course the huge hardware $ saving is why retailers continue looking for the "best" mobile shop and pay application.
Scan & Go at Sam's is a great application. It works in this retail environment as the customer bags their purchases and security is a personal door check. The limitation is that it cannot do self scanning on liquor and other products specified by various levels of government.
A more complete self-scan applications if FutureProof Retail. This work in traditional retail checkout processes, with a BIG focus on loss prevention. One FPR app on a consumer's phone serves multiple retailers.
Self-scanning is great, but retailers must modify checkout standards and processes to make it work for consumers.