Imagine starting a new job and your coworkers are seething that your pay rate is too high. And you have no benefits. And you don't get holiday pay. And some entitled driver comes in cursing at you because his load isn't flawless. And some hs dropout pot head in a polo tries to write you up because you went to take a piss. And then you get your paycheck and the union decided to deduct the entire $500 initiation fee all at once. Meanwhile the payrate they negotiated for you is legitimately lower than minimum wage. Yeah I'd quit too.
There's plenty of other opportunities out there for people. They don't have to put up with a crap job for crap pay.