Most of the tasks require a slightly different set of inputs, so the creature brains are not interchangeable between different tasks. (The same design needs a different type of brain for almost every different tasks)
Also, the even if the inputs were all the same, the creature still wouldn't be able to learn multiple skills and then "choose" based on the task it has to fulfill. It would have to unlearn the first skill and then learn the new task, which effectively ends up being the same as how it currently works anyway.