That's how (most) blockchains work. The transactions are public from the moment they are created. That's how everyone can agree to the current balances, for example. If the balances are hidden, you will need to introduce trust into the system. Anyone can download the NEM or Bitcoin blockchain and see every address along with the totals. Anyone with an internet connection can compile a richlist.

There are some exceptions to this like Monero and Zcash but the above is how most blockchains work. NEM is no exception.