We often worry that our lives may be meaningless, but why don't we ever worry that nonhuman lives may be meaningless?

Or ever give it any thought at all, for that matter? How is it acceptable to throngs of humans that we alone should have souls and survive death, that every nonhuman living thing (animals, insects, and microbes alike--hell, why not plants, too, while we're at it; and all that other stuff, of course) must be soulless and perishable? Why is it perfectly okay for their lives to meaningless and not ours?