[mden]

I think it's more like laws (of man, not nature) than art or math. There are complex rules that define how a computer and a programming language on that computer function. Even if we assume these rules are perfectly defined and not bug-ridden the programmer still needs to understand them and write contracts (code) with no logic errors that can lead to any number of disastrous scenarios such as data-loss, data-corruption, or data-leaking among others.

Take this immense complexity of the computer and the programming language and complex it further with requirements for the business problem being solved and throw in a tight deadline and you have a recipe which leads to the vast majority of code being buggy.