I have wondered why my own kids mattered too in the sense that I already have a policy for insurance that covers them no matter where they are or what they are doing or whether they are with me or someone else such as school or grandparents or the park or whatever.

It could also be the other way around in the sense that if you are busy watching your own 2-3 children then your degree of attention to the daycare children is more limited and therefore they limit the number of extra children they will cover. Therefore it isn't that your own children are covered by the daycare policy but the policy will only cover a few more based on the fact there are already 2 -3 kids in the home.