A meaningful union should always be able to bring things in a company/sector to a halt, and a consequence of widespread unionisation is that they expand to be able to bring the entire country to a halt. Unions revolted in the late 70s because a decade of high inflation had destroyed wages, and the government tried to limit pay increases of any public sector worker, or private sector worker whose company had any government dealings, to 5%, which consituted a massive real-terms wage cut. This was a reasonable response to protect the interests of their members.

The flipside of this is that there's not much of a sense of solidarity in our culture, so when those workers striking meant people had troubles in their daily lives, they turned against the concept of unions. This led to an anti-union government which massively restricted the ways in which unions were able to operate. Simply put, it was a form of class warfare that anti-unionists won because we decide to put our own personal comfort over fair wages and working conditions for others. At this point, it's more of a cultural issue in how we perceive unions.