Maybe because the UAW workers and the Toyota workers are only a buck or two apart.
The work rules that the Uaw negotiated generally fall into two categories.
One is safety related, trying to cut down on death and injury. Even when OSHA came about the union were their defacto in house agents because while OSHA had the clout, they didn't have the manpower.
The other category is trying to get more people employed by making overtime costly. A noble ambition stemming from the sweat shops they were formed to combat, but it probably has something to do with more people working means more dues collected and more power/prestige for the union.
Make no mistake the union's goals are honorable, but all union leadership is elected. They are in the end, politicians. Blaming the membership for the bad apples is like blaming everyone in Illinois for Blagojevich.