It might be a bit chewy for a Monday morning, but Bob at One Cosmos has the answer. You know you want it, as the beer man says at Yankee Stadium.
He does get into Schopenhauer a bit:
"If I take away the thinking subject, the whole material world must vanish, as this world is nothing but the phenomenal appearance in the sensibility of our own subject, and is a species of the subject's representations."
I think I exist to drink wine and to wonder why I exist, after work. After a few wines, one wonders whether one does exist at all, and whether "I" is an illusion. Sometimes, I wonder why other things, like ham sandwiches, exist. The cosmos itself just gives me vertigo.
Image: From the Hubbell scope