For the system administrator, it is a checklist item. Have you disabled indexing? Did you just upload a folder called /private_do_not_index/ without a password? If so, you are not secure. You are just obscure. And obscurity fails the moment a search engine spider knocks on your door.
The search string is more than just a collection of tech jargon. It is a digital cry for help. Every time a user successfully finds a result for this query, it represents a failure of basic web security hygiene. parent directory index of private images full
Most web servers (like Apache or Nginx) are programmed to look for a file named index.html For the system administrator, it is a checklist item
intitle:"index of" "parent directory" : Finds pages showing directory listings. For the system administrator