Now why would transactions from a DEX be linked to your bank account?
Because that's the main use. Transactions through bank accounts.
That would only happen if the exchange is KYC-compliant or centralized.
It has nothing to do.
The smart thing to do would be to buy privacy coins with cash (paper money) in person, and trade them against other cryptocurrencies on a decentralized exchange (DEX).
That's actually not smart at all. If you are only going to buy or sell in person you will have even less chance of executing the sale or purchase, and none at all for someone who does not live near a large urban environment. In addition, meeting in person has its risks.
By the way, spending wouldn't be much of an issue since you can exchange popular privacy coins (like Monero and Zcash) for Bitcoin. You can then use that BTC to load a prepaid virtual card on MoonPay, or simply buy a gift card to spend your coins at your favorite store/retailer.
Not when they are banned And for that I will buy and hold bitcoin simply because it will not be banned, it will give me more profitability, it has more liquidity to exchange and I can use it with privacy if I am careful.