Just the general one that issuance companies make money by taking in more than they pay out. So on average and over time it costs you more for insurance than you get out of it. Only insure for catastrophic losses and to cover your responsibilities to others (life insurance to provide for your loved ones, liability insurance for those you may injure) that you wouldn't otherwise be able to accommodate. Loss of a bike? You can probably just pony up and buy a new one, or do without for a while.
Some find that regardless of the financial logic, insurance provides peace of mind that they value highly enough to make paying for insurance worthwhile.