They have their uses but in my experience are rarely driven by requirements.  The ones I've seen tend to be massively over engineered and have been put in place by people desperately trying to 2nd guess what the customer needs vs the inadequate statement of what they want.  Failure to 2nd guess correctly results in the project being deemed ITs failure for not satisfying the NSRs (Non-Stated Requirements) that were assumed to be so obvious that they weren't specified