What human resourcIs human resource planning only relevant to large companies or should small businesses do HR planning too?

As I personally believe, there must always be a Human Resource agent within any company. However, larger companies may have variable job and personnel classifications and divisions; and smaller companies may have fewer job divisions and one person or a small group may hold several positions and responsibilities. For example, in some places, the founder and owner of a business can be the cook, receptionis, recruiter, human resource agent, etc. So, I believe it is necessary to have an agent of the Human Resource in both smaller and larger companies.

Human resource planning is pivotal for the success of any company. Generaly each company prepares a budget and business plan for each fiscal year, consider it as company's "to do/goal to achieve" now the question arises that how to achieve that "to do/goal"? here comes the role of Human Resource planning like how many resources you need to run the company, Which skills are to be developed to handle the future challenges, How to retain the top talent? etc. 

Each Business plan requires a well worked out HR Strategy (synced with that Business Plan) to excute it effectively.

Regards