I understand the appeal of a digital currency that is decentralized, like bitcoin. But why do we need a digital centralized currently. Isn’t it just money that

I understand the appeal of a digital currency that is decentralized, like bitcoin. But why do we need a digital centralized currently. Isn’t it just money that moves digitally, which already exists? Why do we need to add anything to that? What am I missing? I feel like for this to make sense, the next logical step would be to get rid of all the cash, and I get the whole, make the world cashless so we can instantly control/monitor every flow, but is this really the only motivation/endgame? What will be the difference between me depositing cash at a bank, having my balance update and then transferring it to someone via my banking app? Is is that transfers will be faster bc the currency is actually always held at the central bank and accounts are just claims to it? What is the point of CBDCs?