Here's a very good article by the IDoneThis Team illustrating, with concrete examples, why copywriting is important for startups, and some essential advice for how to get it right. In summary:
- Explain your service using the fewest possible words - every piece of detail is an opportunity for confusion.
- Use help documentation to handle corner cases.
- Users won't read most of the words you write - understand how context shapes meaning.
- Include help text on every single page.
Perhaps I'm biased as a writer myself, but I believe that good writing is an essential skill for entrepreneurs. In fact, I've covered a more general example of this in an earlier article on how to get better at writing.