Why there's so much disdain against depressed/sad/unmotivated people?

It's too common to make fun, get annoyed or even angry with people who are depressed or have this kind of sad or unmotivated personality. People get really nasty sometimes. I remember there was a lot of hate on emo teens when I was younger. I just don't get it? It's not that I don't get it can get uncomfortable if someone it's constantly bringing the mood down, but I don't get the anger or annoyance. How can you get annoyed or angry with someone who's feeling sad?

(english it's not my first language)