I honestly don't understand. If people do side projects and programming in their free time then how is that not an expression of interest? What about the inverse? If someone is not willing to do that then how is that not a sign of disinterest? Someone who only does their job and nothing else is not exactly someone I would call highly motivated or highly interested. There is this misconception that there is an upper bound to how interested someone can be. As if you are either interested or not.