As 
@fossyant says, sadly a sign of the times 
It's interesting to witness the diversity of dracionism across the gamut of Sainsburys stores I visit in varying parts of the world; ranging from "scan your receipt to leave, otherwise it's off to the gulag" to "please, crack on to your chelsea tractor with impunity"..
I think in these times it's important to remember that supermarkets, just like any other retailer need to protect themselves against the growing levels of theft that are inevitable as the cost of living crisis deepens.
As usual those who can least afford it are hit hardest, and it pays to remember that these are often society's least-fortunate, educated or astute. 
As such the bar is set relatively low and one's sense of affrontary can easily be appeased by remembering that fortune favours the brave; and that one can beat the increasingly harsh demands of the system by employing creative and lateral thinking. 
For example one might choose to beat the system by claiming at the self-sevice checkouts that your 1.5kg of Granny Smiths apples are actually a much-lower-value root vegetable, or by creatively secreting 1.5 litres of own-brand gin in one's lower colon and nonchalently John-Wayning it out of the store with impunity 👍
desperate times call for desperate measures - stay safe out there people!