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.
More than once, I've had a conversation roughly similar to the following:
Me: "I want to live forever, of course; but even if I don't, I'd still like for some sort of sapience to keep on living."
Someone else: "Yeah, so? You'll be dead, so how/why should you care?"
I've tried describing how it's the me-of-the-present who's caring about which sort of future comes to pass, but I haven't been able to do so in a way that doesn't fall flat. Might you have any thoughts on how to better frame this idea?