Planning is a wasteful byproduct of being a poor developer. A good developer will write code once, get it right the first time, without any planning, and have it do exactly what it needs to do. Everything else slapped on top of that to get from A to B is a waste of time. That includes planning. Writing tests. Coordinating meetings. Documentation. Commuting. Sleeping. Unfortunately, people have come up with things like "planning" and "QA" because they hire incompetent developers - and instead of properly getting rid of them, they hire people to fill in the gaps and flaws.
Just kidding, sort of.