Several.

Yes, it is true that you must be fully KYCed to use the fiat banking system. But the whole point of bitcoin is to get away from that. I use bitcoin precisely because I don't want a bunch of unknown third parties monitoring everything I do with my money, requiring their permission in order to do it, being censored and having my transactions refused if they don't like what they see, and then sharing that data with anyone and everyone they like. If you link your bitcoin addresses to your real identity, then you remain under constant surveillance. My stance on privacy is well known, and by subjecting yourself to KYC you have exactly zero prviacy.

It is also a massive security risk. Centralized crypto services have leaked, sold, shared, or been hacked for sensitive data an inordinate number of times. Every big exchange is guilty of this. Ledger themselves are guilty of this. Would you be happy with your real name and address being leaked across the entire internet next to a list of all your crypto addresses and their balances? Not only can anyone in the world monitor exactly what you are doing with your money, you become a target for both electronic and physical attacks to have your coins stolen.

KYC can ruin your life. Even without the crypto side of things, KYC documents are sold on black markets constantly. Having your identity stolen can leave you hundreds of thousands of dollars in debt for loans or credit cards you had nothing to do with. The latest studies have shown that identity theft costs US citizens alone over $50 billion a year:

https://javelinstrategy.com/2022-Identity-fraud-scams-report
https://javelinstrategy.com/research/2023-identity-fraud-study-butterfly-effect

I'd also point you towards this thread: Why KYC is extremely dangerous – and useless