Most plastics are still oil based right? As long as that continues oil is way to valuable to completely go obsolete. Probably would be much better off stopping using it a fuel so it can be saved for more practical applications in the long run.
Using it as a fuel is a practical application. Everyone who drives to work is turning oil into economic productivity. A portion of that economic activity is reinvested into societal progress; moreso if the job has positive externalities. A larger portion of that economic activity is re-invested in either human comfort (which is actually a good thing) or wasted. And, honestly, we waste a lot of plastic.