food science question

Consider the following ice cream recipe:

Pumpkin Pie Ice Cream Recipe

Ingredients

1 can (15 ounces) pure pumpkin puree
OR
1-3/4 cups homemade cooked pumpkin puree

1-1/2 cups heavy whipping cream
1/2 cup granulated white sugar
1/4 light brown sugar
1/2 teaspoon salt
1 teaspoon ground cinnamon
1/4 teaspoon ground ginger
1/4 teaspoon ground nutmeg
1/4 teaspoon ground cloves

Directions

Drain pumpkin puree in cheesecloth lined strainer for 15 minutes.

Heat cream, white sugar, and brown sugar at low to medium heat. Do
not boil. Stir often until small bubbles form at edge of pan. Remove
from heat and whisk until sugar dissolves. Cool at room temperature.

Combine pumpkin puree, sweetened cream mixture, salt, cinnamon,
ginger, nutmeg, and cloves. Beat using an electric mixer on
medium-high speed for 3 minutes, scraping sides often.

Pour mixture into ice cream machine. Freeze according to
manufacturer's directions.

Question: Why is the cream cooked? i.e., what is the advantage of cooking the cream mixture over not cooking the cream mixture?

Another question... would it be acceptable to use half-and-half instead of heavy whipping cream? I realize that the final product would have a much less rich mouth-feel. But I think that ice creams vary a lot in fat content, and I think it's a matter of taste, how much fat content you prefer.