I don't know of better way than to let your business give you what you want for your lifestyle. Whether it's a sample business plan for a small business or one where your business gives you a plan, it should tell you what is needed to take you where you want to go and when and how you can get there and it should be in clear simple terms, supported with all the specifics. So using a sample business plan for a small business is just one of many ways to make a business plan but frankly I think designing one that will have your business give you exactly what you want is by far the best way.
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.