De-romanticizing Labor Unions

With the ongoing dockworkers' strike, 'Jane Galt' takes a dim view of the role of unions today.

While there's a certain part of me that revels in the glorious struggle of the unions in the 20's and 30's, I think trying to maintain a unionized workforce in 21st century America is a losing battle. Unions are rigid, combative, and fiercely protective of their turf, the exact opposite of what makes our economy so effective. They made perfect sense when people were just more dexterous horses, as in coal mines, or cheaper machines, as in assembly-line workers. But our technology has made that model outdated, not merely because we can replace workers, but because we can make them so much more productive, if only the unions will allow it...I find it hard to see a compelling state interest in encouraging this.

In her view, government labor law is biased in favor of unions, and she would change those laws.

Discussion Question. Why does it make sense for white-collar government workers to have unions?