This is pretty much SOP in most corporate type retail outlets, IME.
We had an incident at a local Whole Foods grocery store not too long ago where an employee chased a shoplifter (who took about $400 worth of food) and tackled him out in the parking lot, detaining him until police arrived. The shoplifter was arrested, the employee was fired. Line from corporate was that company policy prohibited any employee from touching or laying hands on any customer in the store, even when the 'customer' was a thief.
Corporate does not want to be held liable for anything. The merchandise in almost all cases is insured against theft. The cost of a potential lawsuit from a shoplifter accusing an employee of assaulting/injuring/manhandling/whatever them would be far more expensive than an increase in insurance premiums to cover the theft.