Dr. Sowell answered this question in "Applied Economics". He calls it "Stage 1" thinking. No one looks to the future of what might happen. They don't ask "what might be the incentive for some one else. Why did large corporations like JC Penney & American Airlines m.ove to Texas. New York governments didn't thik what others might do in response to higher corporate taxes.
In the case of union members they are only thinkig of themselves. Have npoticed many of them don't want any younger workers.