The purpose of insurance is not to reimburse an expected loss. The insurance rates will promptly go up to cover these losses. Insurance companies are not charities. Ultimately, the losses will be borne by the business, and then their customers.
It's mainly an accounting hack with little value to negative value for the company as a whole after your company reaches a certain size, I agree. There is the classic idea insurance idea that because retail runs on thin margins, keeping the money flowing is important so the whole house of cards doesn't fall down from a huge decrease at an inopportune time, but the relationship stays around way longer than is necessary because of the social organizational effects above, IMO.
If this was possible, more and more businesses would do it, increasing the cost of insurance (for the insured and for everyone else in their business) until what you pay in insurance balances out what you scammed for.
Sure, maybe one store could do it and get a bit more money than competitors or maybe they just all claim a little bit, part of which is real shoplifting, part is wrong data (whether intentionally wrong or not). Considering insurances are still standing and making more money than ever, what you say can't be more than anecdotal.