Imagine living your life without depending on Banks ever again. Using only cryptocurrencies such as Bitcoin or Ethereum, you can make your own income stream and use the coins earned to buy stuff from merchants who accept them.
Well, then that'll just be like the current state of things were we work for fiat and use fiat. Obviously the benefits is that we no longer need to have the money go through banks before using them and we can keep them ourselves but there might be some services that would not be available to us such as loans (which also means no credit scores, etc). We basically just spend what we have.
Of course once we get to the point where crypto more than half the population is using crypto then there might be more providers to replace the services banks give but for now we still have a use for them.
We'll then realize how it is to have full control over our money. That's what Bitcoin was supposed to do in the first place, right? Though of course, for now that's just wishful thinking and I don't think that we'll get by exclusively on crypto. Too many aspects need to be addressed and considered first.
And with bankers basically controlling most goverments, it's unlikely that we'll see that happen within our lifetimes.