Every business plan should focus a lot on the business's potential competitors, because research and analysis of the competition effectively gives you plenty of useful information. It may guide you as to where you should be advertising and marketing, or certain strategies to use or ones to avoid because you see they have been used unsuccessfully by others.
Now as I said, there are many other reasons too. After graduating from college, I started out in manufacturing as an engineer in a pretty large company and now, 45 years later, retiring as a of Director of Manufacturing, I have discovered an awful lot about business. Not only did I learn and teach a lot about business, I worked with small business owners as well. I've learned that it comes down to this. Too many owners work hard in their business but less on their business.