A lot of this is justified by startups as necessary and most young people are just simply too stupid to know any different. When I see a 25 year old who isn't a founder working 12 hour days constantly despite getting no benefits and actually causing a ton of harm, I can only attribute that to ignorance and stupidity. Usually, he has been fooled by the people running the company into thinking that his work is necessary at the moment and that it will be repaid. It's neither necessary at the moment, nor will he ever be repaid a single penny. In fact, when he stops working so hard, he'll be fired.
As Radiohead put it in the song "Just": "You do it to yourself, you do And that's what really hurts".