Why "should" I like the taste of ice cream?

I do. I don't have to eat it, and I could trade off the fulfillment of that like for other likes. But I do like it, and that enjoyment is a value to me, I won't give it up except for a greater value, and even if I give it up for a greater value, it wouldn't mean that I had stopped liking the taste of ice cream.

You don't need a reason to value; values are the reasons.