What We Lose to Shoplifting
nytimes.com
nytimes.com
Stores made this change a long time ago because it reduced costs and increased shopper throughput, but it sounds like, at least in some places, those economics may have changed.
If the store thinks a specific person has stolen something, they can detain the person until the police arrive to investigate, but they can't detain people for simply refusing to allow a bag check.
The other problem is that stores that do this experience a reduction in the number of shoppers that will go there. That can be worth it, of course, if the practice stops enough shoplifting loss to make up for the lost sales.