If you take out government workers, the number drops to around 12 percent. Some claim that workers in the US are too wealthy and complacent to care about organizing themselves. But it's pretty hard to go for the fat, happy American worker theory when you consider that the average weekly wage, when adjusted for inflation, has dropped by 20 percent since 1970. Then there's union corruption. Some claim this is a reason for union decline.
Goodness knows there's a real problem here.
Most union officials and organizers, being honest and hard working people like the rest of us, are as disturbed by this as anyone. More than enough to pay your dues. It mostly comes down to a question of raw power. The trade union goal of getting corporations and government to accept contracts favorable to their members is based upon the ability of workers' organizations to both threaten and carry out strikes. That's the way to get bosses to share the wealth.