People don't usually notice that DNS exists. They use their browsers and send email, and they assume that they'll reach the expected destination. When they don't, it's alarming. The 2016 DDoS attack on Dyn's DNS servers brought a large portion of the Internet's traffic to a grinding halt. No one expected it, and few people understood it.
IT people often take DNS servers for granted. They perform an essential but simple task, and they're just supposed to work. Most of the time they do, but if they go wrong, the effects can be disastrous. An unreliable server means an unreliable Internet connection. A rogue server can let malicious sites impersonate legitimate ones. DNS monitoring can catch problems before they become major.