ELI5: How does *free* Facebook marketplace scam work?

Every time I post things on Facebook marketplace for free I get a ton of scammers asking for the item/my address. I can tell they’re scammers because their Facebook pages are not local and they have terrible reviews on Facebook marketplace.

Since there is no monetary transaction, Venmo account, etc. how does the scam work? What do they get out of requesting something for free and then never picking it up?

I’m assuming it’s something specific to the thing being for free, this doesn’t happen when I post things for sale.