Because it's the least-likely position to be staffed by a company. It's the "least important" person to have.... until it breaks. Often a company relies on routing-switching engineers to do DNS instead of hiring a dedicated DDI engineer (DNS, DHCP, IPAM). It saves money in the short term, but when shit hits the fan... no one knows how to fix it because DNS is really easy until it's not. DNS is super simple at a basic level. But it goes way deeper than most people realize.