It is insightful because gaming the system is exactly what people do. When someone asks me, "What is your greatest weakness," I typically say something stupid like, "I guess my greatest weakness is that I don't spend enough time with my family because I tend to work all the time," instead of the reality, which is, "I fantasize about having meaningless sex with every woman I meet. Even the homely ones."
When someone asks, "Why do you want to work here?" I might say, "Because I find the way your company puts input fields on a web page to be fascinating, and I want to be a part of it." The reality, however, is I want a damn paycheck and I couldn't care less what the company does.
The point here is that nobody answers these questions honestly. Nobody. So what on Earth is the point of asking them? There isn't one. These questions just fill up space during the allotted hour of interview time, and are used by the interviewer to justify the opinion they formed within the first few seconds of the interview.