Creating a plan can be a valuable exercise in clarifying your ideas. It can also help you understand the scope, amount of money, and time needed to start.
It will help you focus your energy and time on the most likely success.
To write a business plan, you'll need to research your ideal customer and competitors information that will help you make more strategic decisions.
A business plan can be a great way to convey your vision to potential employees and build their trust in you, especially in the initial stages of growth.
It's easier for other companies to see if your business fits their vision and audience. This is especially true if they are further along their growth path than you.
Many business plan competitions offer prizes like mentorships or grants. You can search Google for "business plan competition + [your area]" or "business plan contest + [your industry].