Why are swiss bank accounts considered so secure?

Answer 1

The concept of neutrality was more relevant during the cold war. The primary reason the Swiss banks are preferable to some people is their "private" banking accounts. Traditionally, until recently Swiss Banks never divulged any information about their clients to anybody, even their own government intelligence agencies. People could have numbered accounts without their names and transfer money around. Also they asked no questions about the origins and the nature of the money, even if it is brought to them in cold hard cash. These accounts were perfect to hide money, whatever the reasons, legitimate or not. Nowadays, some governments have succeeded in forcing the swiss banks to share limited information about their clients.

Answer 2

The Swiss are neutral. So, in a war, your money won't be in the hands of the enemy.