Unions -- propping up mediocrity for over 100 years.
If you picture a bell curve distribution of potential workers, where on the right tail are the can-do ambitious and on the left tail are those that no incentive will drive ambition, inside the majority (~70 percent of the distribution) lies the influenceable. This group will respond to incentive: either the incentive to coast and have a guaranteed job/benefits or the incentive to make something more of themselves.
Unions promise above-market job security, above-market pay, above-market job conditions and above-market pensions/benefits. The quid pro quo? Well, you have to do largely the same dead-end job for 20-30 years. Too many fall for the temptation and remain mediocre.