The type system is there to help, not to babysit you. You can circumvent the type system in many ways, not only regarding const, and each time that you do that what you are doing is taking one safety out of your program. You can ignore const-correctness or even the basic type system by passing void* around and casting as needed. That does not mean that const or types are a lie, only that you can force your way over the compiler's.
const is there as a way of making the compiler aware of the contract of your function, and let it help you not violate it. In the same way that a variable being typed is there so that you don't need to guess how to interpret the data as the compiler will help you. But it won't baby sit, and if you force your way and tell it to remove const-ness, or how the data is to be retrieved the compiler will just let you, after all you did design the application, who is it to second guess your judgement...
Additionally, in some cases, you might actually cause undefined behavior and your application might even crash (for example if you cast away const from an object that is really const and you modify the object you might find out that the side effects are not seen in some places (the compiler assumed that the value would not change and thus performed constant folding) or your application might crash if the constant was loaded into a read-only memory page.
