To clap or not to clap, that is the question.
There are a host of reasons why people don't have 50. Some are used to places like Facebook where it's one like or nothing so clicking once is all that they know. Twitter is the same.
Some have gotten the notion that they only have 50 claps a day to spread out over everyone they read so the do so sparingly. I try to squash that notion whenever and wherever I see it.
Lastly, you may want to sit down for this one. The ability to clap or not is just too much power for some people to handle. I'm referring to the internet troll type personalities. And seriously, who cares if they clap or not? ;-)