might obviously be for airdrop purpose, any normal human wouldn't buy an address where private key already exposed, maybe they are interested in the history of transactions from that wallet and probably have found some airdrop that have such eligiblity therefore they are seeking such address.
because after all, even if you do sell your address, you will still see the private key, therefore its security risk for holding any asset, but if its for airdrop claiming they'd just claim and then dump the address immediately.
...I think empty wallet buyer are collecting old wallets with the thinking that any wallet might gives him big profit in the future.
Obviously, these buyers are newbies who have already heard about retro airdrops, but are not yet familiar with security. And accordingly, they do not understand that the former owner can withdraw the contents of the wallet at any time using a private key.
probably they've already considered security but they are so eager to get eligible which might have something to do with address history transactions and just don't care thinking they'd could move the money in the first seconds that most likely be the scenario in my honest opinion.