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.
I love the "Free" listings then you drill down in the description and it says $4500. I responded to a 'free' item and asked is this free? Its listed as FREE. The guy responded no, its not free, I then screen shotted the free listing and asked why he listed it as free, he said its what people want to see. M-F'r...he's right! Yes, respond to an item and crickets.....see it 4 days later still for sale, "will take down once its sold" same as on offerup. You respond and you hear nothing. at least ebay has an automated mechanism where no real time seller monitoring is needed. Seems the safest way to purchase if you can handle the fees and shipping although shipping through ebay has become incredible affordable nowadays when you use their shipping options. Its unreal how they can ship this cheap on some items. Its even worth telling a remote craigslist seller to post on ebay with a fixed price and send you the link just to get their shipping rates and a secure way to buy it.