Why do people refer to Linux as an OS when it is just a kernel?

Why do people call businessmen "suits"? Or say that "planes fly" but not that "submarines swim"? When and where does an aircraft carrier "set sail"?

What exactly is "pre-boarding" at an airport?

https://m.youtube.com/watch?v=vdPy5Ikn7dw&pp=0gcJCdgAo7VqN5t...

Because "Operating systems based around the Linux Kernel, excluding Android" doesn't roll of the tongue so nicely.

Everyone knows that when someone says "Linux" he means a certain category of Operating Systems.

Because Linux is an operating system. Linux can run user-space programs without any user-land.

Because the distinction is meaningless for most people.