It's the same idea as Gambits in FFXII, except automating better. Such macros will have better reflexes than you, allowing you to clear content that may otherwise be too difficult, or at least a gamble on clearing, which is the point of using it for the people that do so. People in IT will do this for aspects of their jobs, taking out the tedious parts by spending a bit of time to automate and test them, so they can concentrate on other aspects.