The HTTP protocol has become the de facto standard application layer protocol of the internet. From publicly available web sites and APIs to “inter-process” communications in REST based microservice architectures or large Service Oriented Architectures based on SOAP, you find HTTP being used again and again, due to its simplicity and our familiarity with it. How many protocols can you name that have memes for their status codes? Of course, such a popular protocol has endless pages written about how to properly monitor the services that rely on it, with many options specific to every use case.
Most sysadmins and developers have at some point used a few of the popular Linux networking commands or their Windows equivalents to answer the common questions of host reachability - that is, whether a host or service is reachable and how fast it responds.