Though on one hand I'm inclined to agree with you regarding Nagios, on the other hand I disagree. What you're missing is the concept of developer empowerment. I am a sysadmin / operations engineer, and one trend I've noticed over the course of the past ten years is one toward developers venturing further and further into what could be labeled "traditional" systems administration. Do not underestimate developer demand. It's fueled many technological "movements" in the past ten years, infrastructure automation being a huge one.