Note the following from the article:
we took science ... to the companies and, without
having to spend time and money involved in a policy
solution, the companies themselves chose to solve it on
their own.
This means that, since the behavior is voluntary, they get to do it on their own timeline. In order to force anything to go faster would require some cattle-prod of a law or regulation, with punitive measures that hurt the bottom line through fines and injunctions.Which points to another possibility: They know how long it would actually take to get those kinds of laws enacted and enforced, and they'll only go as fast as that.
And don't forget, two years is enough time to forget about this. So in two years, maybe they'll simply do nothing at all.