Cryptocurrency:

  - My money is secured by a private key and nobody can touch it ever unless they get my private key. I can simply be cautious about my private key and I know there is no other way anyone can ever get my money
  - I can fill out a text box with the amount I want to send and press send
  - I don't have to deal with some harebrained naming system. I can literally just send to someone's public key. This is literally how cryptography is inteded to work. It's up to _me_ how I obtain his public key.
  - Monero etc exists (admittedly, not sure if it still works when someone has all the mining/stake power)
  - Some guy is getting rich because he owns more miners or stake

Fiat:

  - My password is 8 digits (this is not even an exaggeration, some of the biggest banks in my country do this)
  - The bank might give all my money away if someone knows where I ate KFC last
  - My money may be stolen for other reasons, because the bank wont tell me what data I need to keep private to avoid having someone transact as me
  - The ID they use for authentication was also given to some 30 other e-commerce platforms and cannot be considered secure
  - There is almost certainly a way to get into my account without the password
  - I have to be paranoid and try to keep random trivia private such as how much I payed on an electricity bill
  - I have to type codes from insecure SMS on a phone that I do not want in the first place, because the bank and all e-commerce platforms considers me an idiot and does not even give me an option to turn that shit off
  - If I transfer from one country to another, my transaction may be blocked
  - If I transfer some certain amount, my transfer may be blocked
  - If I use a certain IP address, my transfer may be blocked
  - If I transact at a certain time, my transfer may be blocked
  - If I update Firefox too fast or too slow, my transfer may be blocked
  - If I click buttons to fast or too slow, my transfer may be blocked
  - Someone might hack my computer because it has a Big 4 web browser and the giant stack of software required to support that, instead of a hypothetical OS where people care about security and don't use C, at the cost of some microseconds.
  - If I change my email address (which I don't want associated to banking in the first place) for some reason, my transfer may be blocked
  - When I call the bank, I have to be polite and try to avoid saying anything suspicious (in their own mind) that will make them hold my money yet longer. I will have to supply them will all kinds of nonsense like where I ate KFC last, more ID, and a "phone password"
  - My transactions may be permanently blocked and there's nothing I can do about it because the bank reps just talk to a black box "risk analysis" machine and at some point there's no way to override its decisions
  - Money I receive can be "reversed" for all kinds of bogus, emotional, and/or "risk analysis" reasons
  - The bank can just take my money and claim I was hacked. They have N pieces of my photo ID, address, phone number, email, and much more, and so they can choose a few people they don't like and do this to only them
  - I have to interact with my bank through web pages that crash every 3 button clicks, and PDF files that may or may not render correctly (or snail mail, which is equally full of bad security)
  - Some guy is getting rich because he's positioned a certain way with the bank

TL;DR even if the top cryptocurrencies were effectively centralized by one entity controlling all miner/staking power, I would still want to use them at least for transacting, just so I can have a sane interface to money.