Worth noting that most car drivers have insurance. If you carelessly run over a child, you'll feel bad, but the insurance will pay for all the court cases.
If you run over a child on a bicycle, most cyclists don't have insurance, and there is a reasonable chance you'll have to sell your house to pay compensation to a child who is now in a wheelchair for life.
Car insurance liability limits will be insufficient if you kill someone, and you’ll be on the hook for the remainder. Umbrella will cover you in both scenarios.