Default pictures folder appears in documents folder

I was testing a C++ program that loops trough all the files and subdirectories inside a given directory, and when i tried to list the files inside the default "Documents" directory, I've found out that inside "Documents" there was the default "Pictures" directory, although when I open the file explorer and look inside the "Documents" folder I cannot find any folder other the ones i created. Than I tried using the cmd to search inside the "Documents" directory to see if "Pictures" would appear, and it does. Using the cmd I also discovered that from any of the default directories I can access the other default directories, but when I try using the "dir" command it tells me that the given directory does not exist. I tried this on different laptops and PCs: sometimes the "Pictures" directory does appear, sometimes doesn't, but from any given computer i could access other default directories using the cmd. Can someone explain me this?