Privacy is very important especially for blockchians because they are inherently public, anyone can look up any accounts and there is no protection or privacy within the public blockchains like bitcoin and ethereum. For example, you have an address 0x01 and someone finds out that 0x01 belongs to you and since you only ever used a single account, now they can trace all your transactions and since merchant addresses will be public anyway, they can know exactly how much you have spent at a particular shop and just by looking at how much you have paid, they can know exactly what you buy each day.