Why separate methods for mapDispatchToProps and mapStateToProps?

Question

I'm writing a redux app and I ran in to a small but nagging question. Why is the convention to separate the mapDispatchToProps and mapStateToProps methods? Why not just have one:

mapToProps = (state, dispatch) => {
    ...
}

Answer 1

Because the mapDispatchToProps doesn't need to be recompiled when the state change (it's only called once).