In reality you have to wager it so many times that you'll fall victim to the natural losses that a casino will inflict on your bankroll. However the casinos are banking on you ignoring all the losses and becoming conditioned to playing their selection of games, with all the triggers and habit forming behaviors that come out of it. Even if you do end up with 50 bucks left, they know that you'll likely just return it straight back to them. Quite often they force you to play your deposited money first as well, so you'll lose that long before the "free" cash disappears too.
We have to consider that it's just reasonable for casinos to do so. Being very light and not that strict in terms of promotions will result in abuse. Regular gamblers at that site don't want that to happen as it will affect all users if such big
sh*t happened on that site.
I'm also not a fan of reading bonus terms and conditions but my experience will tell me what's the best thing to do. It's also obvious that big promotions always come with great requirements that's why gamblers should understand that the moment they enter the promotion.
That's why if confused, users can just do normal deposits and stay away from promotions if they don't understand even the basic terms.