Stuff like that makes me want to live. As someone trying to keep depression at bay, I really need stuff like that in the world to happen. And I bet Musk does this for a similar reason. From having watched and read a vast amount of material of him, he's very conscious in what he does, and why. I bet he's had his share of existential crises (the 'what's the point of existing'), hence him having quoted Hitchhiker's Guide to the Galaxy so often. So I bet he works this hard not for the sake of working hard, but to mentally survive (he's quoted saying that laying on the beach for recreation would be one of the most dreadful things he could do), and doing ridiculous stuff like this is part of that.

That said, I find stuff like that close to art, and art is a necessity. Or in the words of Stephen Fry: https://youtu.be/7Ph_AyYMJtk?t=49m4s