Why is the ratio for two rescuer CPR for child and infants 15:2 and not 30:2?

The simple answer is this. Children and infants go into cardiac arrest 99 times out of 100 due to a respiratory problem. While adults are the opposite they go into cardiac arrest usually do to a heart problem. I could go into the complex answer of tidal volumes and occurrence of P Q mismatches but that is the simple answer.