Why should I care about my transactions ever reaching the blockchain if I can spend them while unconfirmed?

From what I understand, I can use unconfirmed transactions because they are essentially already confirmed, they just need to reach the blockchain. This can create a chain of unconfirmed transactions, but that’s fine because they will all eventually be confirmed and added to the blockchain.

If that is the case, why should I care about my transactions ever reaching the blockchain? I don’t see a reason why I should care, and with that, I don’t see a reason to include a fee with my transactions.