That's been the elephant in the room ever since Satoshi published its paper more than a decade ago. When I discuss with cryptocurrency enthusiasts I often get the impression that they think that banks are this kind of useless parasite body that somehow appears like mosquitoes around a pond in summer. That they only serve to basically operate ATMs, send you your Visa card and crash the market every other decade or so.
This is of course a gross misunderstanding of what banks are, what they do, why they do it and where they come from. In particular the idea that "bitcoin is going to kill banks" (a very common sentiment in my experience in cryptocurrency circles) is about as meaningful as "this new type of snowboard is going to kill ski resorts!". No it won't, it might change some things about how they operate but after the transition period it'll be business as usual. Cryptocurrencies don't come even close to replacing most of the services offered by banks. Actually, they don't even come close to replacing most of the services offered by actual currency.
It's this weird cognitive dissonance that you encounter in conspiracy theory circles: the banking system is this hellish beast that steals money from the honest middle-class worker, operated from a global circle of elites acting from the shadows and that must be destroyed at all cost to save humanity. How do you do that? By replacing their currency by your own, they'll never see that coming, those idiots.