...I'm asking specifically when trading.
Since most people associate cryptocurrency with large incomes, identifying you in real life with the contents of your wallet can be dangerous for your health. In addition, most participants of the crypto market categorically do not want to pay taxes, which will be impossible if they are identified.
For most, paying taxes will be the biggest issue since we will be obliged to pay tax depending on the profit we made, and i think its quite unfair. And for others, maybe they just want to retain being anonymous since it will be risky if they know your own identity and the fact that you have lots of satoshis in your pocket, too dangerous to think.
However, since most of the exchanges are already requiring KYC and i know its for security reasons, i'm not already against on it since i'm not doing illegalities in the first place. Even reputable exchanges do so i think we don't have really choices left.