What is the scientific argument pro-straw beyond "yeah sure it doesn't make any difference, but it sure raised awareness of the plastics in the oceans issue! Don't forget the turtle!"
Claiming the anti-straw is unscientific doesn't require that I supply a scientific argument to support using one.
Obviously there is demand for them otherwise capitalist fast food chains would have eliminated them long ago to cut costs. I don't think it's hard to see why they are useful.