For most people, this question may never be completely answered while we live on the Earth. I do believe in angels along with the overwhelming majority of Americans. Angels seem to hold different roles, and some are very personal to each human being. Amongst their many roles are guardian angel and spirit guide, and the parking angel. You can laugh if you wish to, but these roles certainly exist.
I don't know what the parking angel did back before we had cars, but I am sure it was important. I believe it was to help us make connections as necessary. An important roll for these angels is to make it easy for you to test the existence of angels. One must call the angel to get help. Say it out loud, but whispering is OK. Be sure to say "most benevolent outcome" or "MBO". That way, you are not attempting to force someone else out of his parking space. Say "I request the MBO of a convenient parking space at my destination." Every time I ask, I get help parking. Of course, I must ask in time for them to arrange a spot - say ten minutes ahead while in transit. Then the empty space is usually there right as I arrive. Never say "Please", but they like to hear "Thank you."