That is what taking a loan is, you are able to do it, its how you afford your homes etc. The bank is the essential guarantor in that transaction, without the bank the person you buy the home from doesn't trust you enough but the bank has that trust.

So essentially governments build trust with banks so those banks can issue fiat currency. Then those banks build trust with people like you so you can use the bank to issue fiat currency. Its the same system, bank pay interest to central bank for doing that and you pay interest to the bank.

If you mean why you can't get money from the central bank? Its just that you haven't built trust with them. But you can do so indirectly by taking a loan from your local bank, and that trusted middleman takes a fee for it.