Reporting comes at a cost to the store. They've got to have their personnel working on it, possibly managerial staff, and they've got a lot of other things to do, and staffing shortages, etc. If reporting doesn't result in police actions that reduce future theft, it seems like it's a waste.

If retail theft is as endemic as reporting would seem to indicate, I don't know how they could get insurance for 'petty' theft anyway, so a police report isn't likely to be useful. Likely their business insurance has higher deductibles anyway, so it's more useful for major theft or damage, not for smaller claims.