Instead of choosing "unique" spellings, why don't parents give unique names to their children?

I understand that many parents desire to give their children names that stand out and that are creative. Why, then, do parents use (admittedly uniform) unconventional spellings on conventional names to accomplish this? Why don't parents use actually unique names instead? Whenever I see a girl named something like "Britnee" or "Ashlee" I muse on her parents' inferior intellect by choosing a pseudo-unique name instead of a legitimately unique name like Maiken or Twyla.