I use ethersan(
https://etherscan.io/), and just input my address, then every transactions show. Why Ethereum don't need authorization to access user's info? Is it any benefit to do so? I think if someone know my address(maybe have trade with me once) and pay enough time, he can figure out who i am in real world, and even find my secret by analysing my transactions.
Because Ethereum is a public blockchain it's a blockchain that can be read by anyone in this world and anyone in the world can participate in the consensus. Public blockchain are generally considered to be “fully decentralized” and this corresponds to Ethereum to be decentralized platforms that runs smart contracts "applications that run exactly as programmed without any possibility of downtime, censorship and fraud"