weighty ice cream questions

I've glanced at some ice cream recipes on-line and many of them call for cooking a milk + cream + sugar mixture on the stove as the first step. Why cook? What are the advantages of cooking the mixture, vs. just mixing sugar into half-and-half and tossing in the flavoring ingredients? Are most Baitcon flavors cooked or uncooked? Are there flavors that more definitely benefit from having a cooked cream base?