A business that makes sense and is going to be sustainable in the future is one that has that clear vision within which all the smaller parts contribute to make it successful.
It seems to have been put there to fill the need to attribute a certain sum to marketing. Make sure you are researching each point of your budget, make sure that you are giving it context and it makes proper sense within your overall plan.
Business planning process : As discussed above, a successful entrepreneur lays down a step by step plan that he/she follows while starting a new business. This business plans acts as a guiding tool to the entrepreneur and is dynamic in nature - and needs continuous review and updating so that the plan remains viable even in the changing business situations.
You can concentrate so much on essential financials and supply logistics, but overlook other issues like marketing or opening times. By showing the plan to someone you trust, they can have a look and see what might be missing or worth developing more. Getting that valuable second opinion on how robust your idea is will put you in a much better position to start and keep going successfully.