The Life and Strange Adventures of Robinson Crusoe, also known simply as Robinson Crusoe, is the story of one solitary, individual man who is stranded all alone on a desert island. As he's the primary character in the book, and it's his development as a character we're concerned with, it makes sense that his full name would appear in the title.
The "Life and Strange Adventures" part is perhaps then less important, but not altogether so. These words indicate (especially to 18th-century readers) that the novel will be filled with action ("adventures") in far off and exciting places ("strange"). No wonder it flew off the shelves!