• The owner sells the company
• The company goes bankrupt
• You wreck the company van
• The owner goes through a divorce
• You miscalculate the length of a wire pull
• The owner passes away
• The owner gives the company to their children and they don't realize what a valuable employee you are
• You ask for a raise
• The boss's nephew wants your job
• You get your 3rd or 4th period Apprentice Upgrade, then you are replaced with a First Year Apprentice.

These things could also happen at a union shop. But the difference is that when you lose the job that seemed so secure, you can start your next job at the same wage and benefits scale without negotiating with your new employer.

That's because your real security is in the process of collective bargaining.

When you are out of work you have the opportunity to work in any IBEW Local across the country that has work. When you get there the best wages and benefits will be waiting for you, and your benefit contributions can be reciprocated back to your home local.
If you are out of work and don't want to travel you can salt while you are waiting for the next union job.