The job of a security guard is to observe and report. Let the multi-billion dollar companies like walmart and home depot pay for actual law enforcement to be on hand when a security guard observes a suspected shoplifter. The security guard isn't paid enough or trained enough to get physical with customers.
I had never heard of 'shopkeeper's privilege' but looked it up [1] and yes, seems to be a real thing in the United States and nowhere else, according to a quick scan of that wiki article.
More evidence to me that the US was set up to serve corporatist interests over pretty much everything (and everyone) else. Why else provide shopkeepers with some special legal status? (Which again, they don't have in any other country.)
Shopkeeper’s privilege exists as long-standing common law doctrine for a reason. No business should be forced to tolerate theft, or be forced to pay off-duty police officers to prevent it.
And no one is compelled to be a security guard; if the risks and pay don’t align, they’re free to walk away.