

I once sat and chatted with one of these guys waiting for a bad downpour to stop. Being stopped sucks, I know, but here’s some insider information:
They are stopping you for appearances. They absolutely are skimming your receipt, they really don’t care about you personally. It’s all circus.
If they are looking, they are looking for the big loss items. That TV that gets rung up in the back, was it actually rung up? The water case under the cart coming from self checkout? Another big loser for the company. Coming with a tote or loaded cart from the wrong direction is a little obvious to everyone.
Every other stop is for show. To remind the tote runner they are watching. To make the TV thief skittish. It’s all about appearances and breaking down resolve. The door guys can’t stop you, but they can make you afraid that they are vigilant and someone who can is waiting(and the salarymen can, shopkeeper’s privilege apparently in the US). It does work, loaded carts abandoned near the doors apparently testify to the effectiveness.
Some door hosts get by with being passive, they are supposed to be pretty chill and friendly, and dial up the theatrics when someone is reported to be suspicious or when a “frequent flyer” walks in. But that just makes it seem discriminatory and unbalanced so apparently some managers want the theatrics 24/7 to avoid the complaints of unfair treatment.
I understand that each state makes adjustments to this which may grant more or less powers, but here’s a Wikipedia on the overall concept:
https://en.m.wikipedia.org/wiki/Shopkeeper's_privilege
So for example during the aforementioned security theater at the doors, someone who is legally a representative of the company ownership(generally the managers making salaries are bonded to this) is doing their best to catch someone in the act of stealing, putting something in a coat, loading a cart and bypassing the register, etc, and this gives them grounds for some mild detainment. This apparently covers them stopping you at the door or firmly requesting you join them in their office to clear things up(and wait for the real authorities), and means no one questions if they grab the cart which is company property and doesn’t let you leave with it.