Aside from the actual protocol, it makes a lot of sense to have a standardized, discoverable protocol.
Because the alternative, as proposed in the article, is that an agent researches an API/CLI/UI, builds software to interact with it, and then runs that. Every time again. Not only very inefficient, it's unpredictable, and often slow.
Just last week I had an MCP that was down (my mistake) and the agent "decided" that in order to finish my request, it needed to create a python script, refactor that, debug that, and then use that, so it could access my notes (Joplin) over the API and write it's weekly update markdown there. Somehow the thread produced a python tool with over 400 lines of code, five files. It, at some point, even considered putting all that in a git repo. And went on a side-quest to run docker containers.
With the MCP, this job typically takes between $0.05 (Mistral) or $0.90 (Claude Opus). It now cost me $17.00. It took nearly 30 minutes. To write a note in Joplin!
MCPs, or any de-facto standard/pre-known protocol, makes operating on external tools and resources cheaper, faster and above all more predictable.