Lots of good answers on this thread. I think the fundamental underlying reason is that programming
is difficult and so poorly understood. A given: all softwar

Lots of good answers on this thread. I think the fundamental underlying reason is that programming
is difficult and so poorly understood. A given: all software has bugs. Usually, that doesn't matter — a CRUD app will eventually get debugged enough to the point of usability. (Sometimes even maintainability.) We do not understand enough about programming to guarantee perfect execution in all cases, but no one gains any value by causing an obscure input case to cause a null pointer exception. Whenever we use crypto, however, we inherently have code which protects something valuable: from forum passwords to credit card numbers to state secrets. This means that all the subtleties which break in ordinary code, but no one cares about, suddenly become important. Every interaction of input to memory to processing to storage (to network) must be scrutinized for places where a crucial piece of data may leak an encryption key, or perhaps just enough known plaintext of known cyphertext to mount an attack.