Hmmm. How about no other program has ever required this? A program is not the company. I do not need to give away my right to my data to use a telephone or send a postcard.
Postgres also had the advantage of great support for JSON elements, which gives you the power of a no-sql system like mongo in the package. A major selling point if your schema is evolving.
“Educational purposes”.. because everyone knows it’s good educational practice to spout utter bullshit at people wanting information.