One member recently opened up a topic in Services section wanting exactly that, to buy empty ETH addresses. Here is his explanation and its probably true.
Basically I want to participate in new incentivised testnets and they tend to reject wallets that are pretty recent as they think you might be a bot.
Which is why I'm looking for old wallets preferably with activity
Hope that clears things up

And the fact is I try confusing one of them that the wallet they bought doesn't entirely belong to them, because the sellers still have access to the wallet since they know the recovery seed.
True, that seems like a logical problem and he had an anseerr for that too.
The testnets I want to do, you deposit crypto on their platform and the wallet is just used to sign messages and approve transactions so it's not a huge risk for me