It is extremely arbitrary
What Are You Doing Medium?
Alex Valaitis

Indeed. For me the reason is partly this: We usually clap in a concert hall or something like that, we don’t clap alone. What tells you when to stop clapping at a concert? It’s usually when you sense the others are stopping too. (There’s no counting, no reference count.) When clapping online, there’s no signal to guide us.

One clap, two clap, three clap, forty?

By clapping more or less, you can signal to us which stories really stand out.