They bring the ability to open doors that are currently closed. My co-founder who has not written a line of code has been instrumental in our success. When I'm coding she's talking to customers, talking to investor, etc. They bring a different perspective and insight into the product. For the most part we are not writing software for other coders we're writing for customers. A person who doesn't code IMHO is always going to be a little closer to the mark than someone who lives and breathes code. In short, they avoid your company having a monoculture.
We should stop treating programmers as introvert types who are all the same with the same (mono) « culture ». Developers can have different personalities: great coders with great social skills exist. They can bring a different perspective and insight into the product as well. Frankly I don't see much room for pure « biz » guys when talking about technological business venture. ;)