Extracting is the opposite of deleting, and often the safer one
When you want three pages out of forty, saying which three to keep is far less error-prone than saying which thirty-seven to remove. The result is the same document either way, but the instruction is shorter and easier to check.
Page order follows what you select. Type 7, 1, 4 and you get those pages in that order — useful when you are assembling a document rather than filtering one.