Why is it so hard to buy parts from people

Trying to purchase parts from people on Craigslist or Facebook marketplace is so difficult. You can't get them to respond but adds say if add is up part is still for sale. Even when you can get someone to respond and setup a day and time to go to purchase the parts you can't get them to give you an address or a place to meetup so you can purchase these parts. But the parts are still for sale.
How was your FABO experience?