Yeah, because they suck. Uh, pun not intended. Paper straws get somewhat soggy and feel bad in your mouth. They are inferior to the plastic straws they purport to replace, so people resist them as much as they can.
If you want to actually make a difference with an environmental effort, you need to make something superior. Nobody makes fun of LED light bulbs because (up front cost aside) they are wildly superior to incandescent. People actually like having LED bulbs and seek them out. The same cannot be said, and likely never will be said, of paper straws.