Homeowners Insurance and Pit Bull Breeds Don't Mix

Homeowners pay to gamble that they will not need to file a claim. Insurance companies gamble in order to get paid that they won't need to pay. Insurance companies will not gamble, however, on your dog if it is of a particular breed. They will simply not insure your home. Aren't the insurance companies gambling that the homeowners they already insure won't ever acquire a particular breed of dog such as Pit Bull? Aren't they gambling that new homeowners that they insure didn't lie to them about the breed of dog they own? Aren't they gambling that their inspectors will catch on in every instance of 'illegal' dog ownership? Is it therefore pointless for insurance companies to ban coverage for homeowners which have particular breeds of dog or do they just want to test our poker face?