Free stuff is not easy to give away online, and that’s true for second hand clothes as it is true for learning programs.
It’s probably because the buyer does not perceive any value. It’s easy enough to raise one’s hand and say “I am in”. But as soon as life gets in the way, something that is free is just not worth any hassle.
If you have something you need to get rid of, or an idea you are proud of and want to spread, that’s something to take into account.
For as counterintuitive as it might sound, free is not always the best bargain.