why not recylce plastics?

I am reading a magzine article about bioplastics. the picture shows a mountain of soda and water bottels etc etc and talks about some garbage island of plastic floatin in the pacific. Why cant all this plastic be put into boilers and heated until it melts. I am not saying to burn it just melt it until it becomes a slurry again. Then reuse it in stuff that does not come in contact with the mouth if there are FDA problems. Make things like those Tshirt baqgs from the supermarket or trash bags or make the hard brittle plastic they shrink wrap everything in and slices your fingers off trying to get it open.
They can make all the plastic junk parts on a cheap car from this stuff. I am not a rocket scientist so dont know why industry does not do this already. There has to be a reason they dont, any one know why?