Firstly most businesses as of today don't accept Bitcoin and that is the number one challenge that Bitcoin have in regards to eliminating the banking system. Banking system had been in function for ages and people feel very comfortable to do their financial transactions through them. It is sad that people who use Bitcoin for financial transactions are flagged as money launderers, their transaction history can be traced at anytime as if traditional currencies are not mostly used for money laundering. This is one of the major reason why people hodl Bitcoin as investment to make profit, I don't think that Bitcoin can rival the use of fiat in the future.
The main reason why we want to hold bitcoin as an investment is because we are attracted by the huge returns it can bring. Let's not blame and make excuses that because bitcoin transactions are often considered money laundering or businesses don't accept it, we can't use bitcoin as a currency.
I bet even if businesses accept bitcoin or governments allow it as a legal means of payment. You, me and many others will not want to use and spend our bitcoins either. Simply because for us, bitcoin is an asset, an investment that will make us rich and no one wants to spend it.