They are cowards, like all corporations
The liability aspect rules. A jury judgement can cost a lot more than any money saved by catching shoplifters. The shoplifter or guard can be injured which could cost a bundle. If the shoplifter is the right type he/she/it can scream discrimination and sue for a ton of money. I'm not saying it is morally right, but it is the correct business decision.
Cowardly arguments all.
You either support the right thing, or you don’t...
Best Buy and most corporation don’t, their justification for it are just excuses.
The guard is insured under worker’s compensation. The thief may sue if he is injured. But as someone wrote upthread if the policy is not to touch or pursue thieves, then a well organized group could clean them out.
I used to shop at Fry’s electronics back when it was better to build a computer to your own specs than buy off the shelf. But the store was pretty much double-walled in. You couldn’t leave without going through the checkout line, and then having your receipt examined in the exit line.