The point is to increase the cost of the plastics to the point that alternatives start to actually be competitive. And really, we're just making them actually pay for some of the externalities they're getting a free ride on.
If you use government to increase the cost of a thing to the point alternatives become cheaper, most businesses are going to switch. They aren't sticking with plastics out of ideology or anything... it's just cheap. And it shouldn't be.
Fair point.