This is a prime(!) example of a really powerful kind of first-mover advantage. It will be difficult to overcome with communication or advertising.

I remember Amazon's policy, like millions of others, because of a little shot of dopamine in my 20s. Amazon was the first to do it; we all discovered it and it seemed like a bit of the future.

I've used Wal-mart shipping, but couldn't tell you what the policy is, because it didn't strike me as new or unusual when I ran across it. I'm not sure you can communicate out of that hole in my cohort.

(Now, you might change my behavior if you convince me that Wal-Mart is better about weeding out counterfeits; that's new information).