1.) Swirly or bendy, spoonbottom or candy, they are kind of fun to drink out from.
2.) Straws are something of a preventative measure against spills. It’s a lot harder to dump a non-tilted cup all over one’s self.
3.) Straws protect teeth, both the coloring and the enamel.
4.) You can bend them into things and make stuff.
5.) You can use them to suck out the air from baggies, as sealing them.