If you think that P2P transactions without the need for KYC verification completely preserve your privacy, you are mistaken. Such transactions may be untraceable, but we cannot be sure that our counterparties are not passing on information about transactions to third parties. So, privacy is only preserved within the Bitcoin network. As soon as you exchange Bitcoin for fiat money, your privacy is at risk. The only way to maintain privacy is to conduct a P2P transaction through a secure meeting. But if we exclude cash, such transactions are impossible.
What about crypto-to-crypto transactions? You would exchange "coin A" to obtain "coin B" in an anonymous manner. Only works on privacy-oriented cryptocurrencies, though. Something like exchanging BTC to XMR (or vice versa) would do the trick. The only issue would be trusting the other party not to disclose your private information. Would you imagine doing a transaction with an undercover government agent? The fear of getting caught, is another reason why people avoid Bitcoin. Especially in countries where it is illegal.
El Salvador opened its doors to the cryptocurrency. But it ultimately failed out of lack of convenience. People want something that's stable, offline, and easy to use. And what better way than using "good-old" Fiat? As long as cash exists (coins and paper money), don't expect people to use Bitcoin as a currency anytime soon. Our only hope lies on governments abolishing cash for good. With CBDCs and stablecoins becoming a thing, Bitcoin's use as a currency will increase. At least, that's what I hope.