Without being emotional on the issue, will throw in $.02 worth...
If all contractors were like Electricguy61 there wouldn't be a need for a union.
Brian John also makes some serious, and valid points.
Allen also makes some interesting points. According to a lot of posts, and the economic climate around the country, it's competitive from both fronts.
To me it's a question of balance of all the above. Kids coming onto the industry don't have a clue to save (money and insurance) for the future, or where to start getting trained, old dogs often wish they had a security blanket under them (pension).
Unions, while not perfect, do still cast a big shadow within the industry. Ebb and flow of membership through out history is interesting in regard to hows and why's of growth and recession in regard to industry, politics, and control.
Best comparison I can make to make a long story, short (albeit for way different reasons) is we need the unions, like America needs the military. Both serve way different functions, but both cast a positive light in the long play of things.
I worked open shop from 1980 to 86, joined the union in 86, and has been a good thing overall for me. While it's not for everyone, it works well for most. Off my soapbox, but that is my $.25 worth.