Because I don’t use it. Seriously, this article from the Wall Street Journal offers several reasons. In essence, it doesn’t meet the Warrant Buffet “Stable and Understandable” rule. Specifically, the WSJ article states
“You don’t understand Twitter. Few people do, really.”
Proceed with caution.
Efficient Minds™ 
It’s better if you understand the company. But In this case, Twitter is one of a kind, just like FB or NLFX, and you don’t have to understand it in order to make a (short-term) profit. Peace out.