another question is, do we know those address does not have an owner?, I mean the owner has lost the key and can't access the address anymore?.
In my opinion.
I don't think this is possible since we don't know the owner of each address we probably connected one address to another address as happened on Hot Wallet in Centralized Exchange but for personal wallets, it is hard to know it.
I often hear that we shouldn't save on one address for safety. But, I think it's useless too if spreading it to many addresses but still using the same word mnemonic seed on 1 wallet.
I think when you have too many addresses with different mnemonics will confuse you when try to move the money
. However, In my cases, I use a bunch of different addresses sometimes with different private keys for Airdrop purposes . cold wallet only needs one