Why does Wikipedia interlink? Citations which is exactly what Google says it is looking for. Why do other sites interlink? Many do so for SEO which is what Google says it is going after. It all comes down to what is best for your users/visitors. If people come to your site and are click happy because you are offering them what they are looking for, Google will love you. If they come to your site and see a bunch of interlinking that distracts from what they are looking for, then Google will hate you. Your user metrics will show the difference.