That is one reason that a 4473 should be done even for a personal sale. If you sell the gun and it gets used in a crime then it's going to be traced back to you and you'll have to explain your way out of it if you can. If you have a retailer do a 4473 transfer then you're free and clear if the gun is used in a crime. It will be traced back to you but they can pick up the trail again at the dealer that did the transfer for you.
An FFL transfer is, and should always be an option for a sale to anyone the seller (or buyer) has concerns about.
It's required on many sales when ownership crosses a state border.
It protects the seller, and also protects the buyer from buying a stolen gun.
I, as a buyer, or seller, might use the option of an FFL transfer, if I really wanted to do the deal.
However, by definition - a 'transfer' is anytime someone else takes possession of a firearm from someone else.
If I want to sell to a friend, or someone I know, or lend a gun to a friend, or family member, having to spend the money on each transfer is ridiculous.
It's on the seller to ensure the buyer is not a prohibited person.
Similarly, it's on me as a buyer to not buy a stolen gun.
In short: if I choose to take the risk to deal with someone, that is my decision to make.
Some sellers will take 'due diligence' and copy a buyer's driver's license, and carry permit as a record of who they sold to.
Some buyers will insist on the same of the seller.
I will show anyone my DL, or carry permit, but they won't be recording my personal information.
Personally, I won't allow just anyone a permanent record of that much of my personal information out of concerns about id theft.
I have no idea what they will do with it, or how securely they'll manage that info.