Business plan as a decision making tool for projects

As a professional of the 21st century, would you be surprised to know that, traditionally, business plans were not included in the typical project to-do list? Regardless of this unfortunate antecedent, experts in the field of project management who have practiced and taught this discipline for many years strongly recommend including a business plan when setting the basis for a newly assigned project. Moreover, they think that it might be detrimental not to include it as it might hurt the business by leading to non-optimal and often, senseless constraints.