Why all the transactions are visible to all the nodes in the blockchain?
In case of blockchain there are no central systems like banks which list all the transactions in their ledgers in a centralized manner, instead here there is a decentralized (or distributed) system which involves all the nodes. So if you have to store/track/validate a transaction that should be through all these nodes only. Therefore, everyone should have the complete knowledge of the system. Or in other words, the system needs to be transparent enough, so that everyone can see what is happening and can differentiate between the “Good” and the “Bad”.