In most cases, it may be the fault of the person owing bitcoin to lose his coins by not being serious in storing his private keys. Yes, people know that they must use hardware wallets, personal wallets and paper wallets to secure their wealth, but no one emphasizes them that storing and securing your keys is the most important thing after owing the wallet.
I tend to not share the same view. I've found fiat filled wallets in the past, and have usually handed them into the organisation they've been left too or someone with a little more authority than myself. Same goes with private keys or seeds. If I found one, I wouldn't claim that money for myself, however there's definitely a concern on how to handle it due to the moral implications. I probably, wouldn't even check the balance, as that would have the same moral implications.
People make mistakes, and I'm certainly not expecting everyone to be a security expert. When I make a mistake in life, which is inevitable, I hope someone will be willing to help rather than to exploit that for personal gain.