If everything goes swimmingly then yes, it seems unnecessary but if it doesn't all go swimmingly then insurance is the net there to help you. Take Anna's recently uninvited and definitely unwanted visitors... her insurance is going to help her replace the electrical items she lost (not unfortunately the camera memory card). Otherwise she'd be without them for longer than a few weeks :(
The same as a business, should someone decide that your product arrived in poor condition or even worse never turned up then the insurance you paid for when posting it helps you reclaim towards that loss and perhaps even covers making a new product and resending.
But it's not only product or belonging insurance a business needs, no there's liability & other areas that we need to cover ourselves for. In this 'have you had an accident that wasn't your fault' TV advert soaked society, I wouldn't dream of erecting a gazebo or table at an event without the insurance to cover me for any accidents that may happen. A table can be heavy if it gives way... and if it fell on someone's foot and they decided to seek compensation then I'd need my insurance to back me up!
So not mundane or unnecessary at all. When you need it insurance is the safety net that catches you when accidents happen. If you run a small business then it is a necessity.