yes it provided the employees that were still employed with greater protections, but it is not the utopia you seem to believe it is
Did unions improve the lives of members? They certainly did where I come from. American labour history is more complex (union corruption and take over by organised crime seemed to run deeper)
But then i can also point to examples where they did not, where they ended up driving business out, bankrupting people
Where unions are more focused on their own political power than helping workers
Or even if in general the union helped the "average worker" the collectivist nature of unions means not everyone will be better off. For example Seniority, and "personal connections" are often more of a driving factor in Unions than merit or work performance. In fact highly efficient hard workers are often driven out of unions or forced to "work slower", etc.
The answer to this is not airy theorizing or anecdotes but statistical evidence. There are many people who do this. See for example figure 9 here:
1. Their own struggles aren't new: companies have been trying to fuck workers over since time immemorial, and 2. There is a well-known solution to these problems: unions.
Are you working 16 hours a day, barely able to afford rent + food + utilities, and slipping further into debt every day? It doesn't have to be that way, and we have a really good idea, based on historical facts, about how to fix it.