This one is a bit arguable. the definition of public domain varies in different countries.
I think 70 year old rule applies to USA or sth.
if it's public domain and free for everyone to use, why not use it?
for example if there is a free MIT asset pack in itch io why not use it?
isn't the concentration of Pygame jam on the code and programming?
why focus on making assets?
I for one have no Idea how to create sounds, or create a character sprite that can do anything even walking.
What could possibly be the reason?