Isn't It Possible That Nothing Really Matters?

The idea that, ultimately, isn't it possible that nothing really matters at all. Nothing really has any meaning, at least on the level of the universe. We've all entertained this world view before. Why would anyone work so hard to reinforce a world view that's so pessimistic? I mean, who really wants everything to be meaningless? What possible benefit could they be getting from that? When everything is meaningless and nothing really matters, then you never really have to grow up and accept the responsibility of the moral weight that you carry with every decision you make.