That requires tracking individuals, which doesn't work for brick-and-mortar stores (yes, those still exist... ;).

you very much get tracked by brick and mortar stores, not all but many. Just did a return tonight, and once again had to give them my information in order to complete the return. depends on the situation of the return, whether you had a receipt or not, whether you were already on file, or if you had paid with credit card and they could track that.

And all those caveats are why Amazon can catch return abusers while brick and mortar stores have a much harder time, and ultimately don't bother as its not worth the effort.