All of those guarantees are under threat of legal punishment enforced through court systems.
All of those guarantees are given to you based on good standing with various institutions. The bank, the intermediary, the seller.
If you were a person who was not in good standing with a bank, but you still had the money, could you have completed the transaction?
Technology has a trend of destroying middleman industries, as they don't provide value and take a portion of the proceeds for themselves.
DeFi, in this case, is targeting the financial institutions because we now have technological means to replace banks and lenders. Does that mean this process is smooth? or ready for mass adoption? Not necessarily, but the destruction of banks by technology is inevitable. It's just a matter of when