They're unique. Zettelkasten titles can be quite long: "Practices for nurturing healthy brain development during pregnancy" takes up a lot more space for a link than a 14 digit ID. You may say to just use a keyword of the title instead of the whole title, but then it is no longer unique and you must come up with another way of identifying which note it links to.

Also, using IDs means it is very easy to visually scan a note for links. The [[##############]] format stands out vividly.

I like it, it doesn't bother me. Do whatever works for you.