The insurance company has to pay for the cost of the coverages provided to the insured businesses. The predictability of these costs will vary based on the type of coverage. Some losses are immediately apparent (e.g. fires) while others take years to become final (e.g. court judgments for liability coverages). Various expenses, such as getting customers and administrative costs of running the business must also be paid. Investment returns on premium dollars not yet spent add to the available funds to pay these expenses. Insurance companies judge all these and other factors including competitive forces, the legal environment, the investment returns likely to be earned for some years in the future. Then they set rates that make for a profitable operation, subject to regulation by the insurance departments.
Some types of package coverages such as business owner’s policies are underwritten by class of policies rather than as individual companies. If your business fits in a certain classification the whole group of businesses in that class is underwritten together so that rates are set for all of them rather than considering each individual company. This leads to more efficient underwriting and helps to keep the rates low if your business meets the requirements to be accepted in one of the classifications. It also means that such policies have less flexibility than you would have if you purchased individual policies for each type of coverage.