I believe less than 5% of the economy is unionized...not sure we can say they are "needed".Unions are necessary, and I think alot of the good they do is easily overlooked/taken for granted. Their negatives are a lot easier to focus on, especially when you're looking for a reason to hate in service of an ideological position.
I could be wrong on that, but either way I'd like to see what today's economy would like union free.