I don't understand unions. Why not, I don't know ... just look for another job if you don't like the current one? If you are as valuable as you think, then you

I don't understand unions. Why not, I don't know ... just look for another job if you don't like the current one? If you are as valuable as you think, then you should find a better job in no time. If the firm is in the wrong, people will follow suit and the company will fail and competitors which treat people better will thrive, no?