Plastic and paper?

How come some countries are still using plastic bags instead of paper bags in groceries even when we all know how dangerous plastic/styrofoam etc. can be for our environment? Why is plastic and kinds like it still being used so excessively? you hear alot from influential people and organizations about how we need to recycle, reuse and reduce and take care of our environment for future generations but why is it still going on? who's stopping manufacturers from excessively making things out of plastic? who's letting them? Can't anybody come up and invent a replacement for plastic this and that? thanks c",)