What is the importance of obtaining a business license for my future electrical company?

Are you asking the question about an actual company that employs people or about being an electrician as an individual? If you are asking the question about an individual obtaining a license, then for one thing, having an electrician's license shows that you have gone through the proper training and have taken the tests that you will need to pass successfully in order to obtain a license.

It all depends on the locality(ies) where the business is to be established. If they require businesses of your size/revenue to be licensed and discover you are unlicensed they shut you down/take other legal action. Competitors may sic the licensing department on you if you are stealing clients. A business license may also be required to get other licenses/permits.