Block explorers help organize the complexity of blockchain data and make it easy to interpret. For example, with a block explorer, a user can check the history of transactions and even verify the contents of a smart contract.
While Etherscan is one of the most popular block explorers, it has a few limitations. It's not customizable and doesn't support multiple blockchains. Besides, since it's a closed-source solution, users often have concerns about how transparent the system is.