I think the unions simply realize job loss will come along with this type of effort. Better to have a job with a good benefit package that includes employer contribution to health insurance than to see those companies put out of business by another unfunded mandate.
Look at our own GC School District. Ten or more years ago the teachers went on strike because they were asked to contribute toward family healthcare. Now, a decade later the district is laying off teachers because of inflated costs. Ask some of the laid off employees if they wouldn't give more toward that insurance now to get their job back.