In bitcoin, you don't even have promises. All you have is faith that some anonymous people will trade things that you can live off of for your bitcoin.
Maybe some people don't want to be part of a fraudulent, built-to-corrupt system where their money is inflated as there's demand for new loans. Maybe some people just want to use something that leaves room for questioning; that its usage is not forced to satisfy ones' interests; that provides free speech and freedom of choice.
There's a difference between trusting a system and having faith to a system: No one forces you the latter. You ought to respect those people who have different political beliefs than you. No?
So, you would rather trade your car, house and bike to anonymous people for a number. And then have faith that in five years other anonymous people will voluntarily give you the equivalence of your things, than to have a guarantee in the capital of the banks, the loan contacts/collaterals of the borrower and legal enforceability that the equivalence of your things will be returned? All that because someone people in the banks are corrupted? And because borrowers are "forced" to return you the equivalence of your things?
You know that one can live off of numbers written on bank notes, bank accounts or blockchain. That's why the banking system ensures those who invested in bank notes or bank deposit, get back the goods, services and labour from the borrowers who at the loans issuing received those things. That's the purpose of collaterals and loan repayment. With loan repayments, the borrowers pay the debt in numbers to the banks and the debt in goods, services and labour to holders of bank notes or bank deposits. So, the banking system protects you, it ensures that you get back the thing you can live off of. In the bitcoin system, all you have is faith that you will get your things back. Without other people voluntarily give you something you are left only with a number. And now the crucial question: once you voluntarily trade me your house for a mere number, why would I give you the house back? Or other things in the equivalent value?