I suspect people think that 'unique' is a synonym for 'interesting' or 'attractive'. Otherwise it doesn't make sense.
I know two people - father and son - with
Connor as a middle name. The father got it because it was or had been a family ln (there's an Irish connection) and the son of course got it for the same reason. Neither of them have ever used it other than as an item when they fill in forms.
So, my feeling is that if it's a name with personal meaning, then it's fine. Family lns certainly tick that box. But using it, and other lnfns, as if it was the equivalent of
James or
Michael seems either unimaginative or pretentious.