A lot of people do it for selfish reasons (in a good way). For example, say you have a website which surfaces information about specific CPU instructions. If y

A lot of people do it for selfish reasons (in a good way). For example, say you have a website which surfaces information about specific CPU instructions. If you provide an API hook into this information you can expose it to potentially thousands (millions?) of people searching for it on DDG. You then provide a link back to your site below the information. This is an excellent way to get traction early on. I did so with searchcode.com and DDG was my number one referrer for a long time, providing me with a steady stream of traffic which helped it get noticed.