there are some banks going bankrupt so i believe there are a lot of people who lose their money though we cannot do anything about it
That might be true in some underdeveloped countries. But American and European governments provide depositor insurance for banks. If banks in those countries go bankrupt, the depositor insurance reimburses depositors up to a certain amount. In the U.S. the insurance is for up to $250,000 per depositor per bank. That means if you have accounts at 10 U.S. banks, you can be insured for up to $2.5 million.
Insured U.S. bank accounts can include individual retirement accounts. Those bank accounts allow the depositor to invest in the stock market. Banks also reimburse their customers if their accounts are hacked. Bank cards protect customers who make purchases by allowing chargebacks.
By comparison, bitcoin provides no insurance and no chargebacks. Many people lose their bitcoins because of problems with their wallets. The latest big loss was the Bitfinix fiasco. Bitcoin losses happen regularly.
In American and European countries, people don't lose money in their bank accounts. It's delusional to think risky bitcoin will replace banks. The extreme majority of people aren't that naive to trust bitcoin instead of banks.
The conclusion will be banks have already establoshed their trust on their customers. The fact that they havr been there for a lot of years makes it impossible to wreck it. They took well of their accounts and gave some features that will let them see that they can really trust them. Just like those insurances.