wontfix, working as intended. The startup wants you dependent on them for everything and to spend nearly all your waking hours inside their office so they can coerce your loyalty.
I don't know if it's to coerce loyalty. I would presume that the main motivation is that they know that you are what generates profit. So if they can exploit you as a profit-generating resource, and get away with it, they will do so. This isn't novel. At the beginning of the 20th century, it was common for entire families, children included, to work 16 hours a day, 6 days a week, and barely earn enough to survive. That was not done out of economic necessity. When the government stepped in and required companies to pay 1 person enough to raise a family for 40 hours of work in a week, that essentially amounted to requiring them to give a greater than 960% wage increase. (Going from getting 384hr of work out of a family of 4 in a week to getting 40hrs of work from that same family, just to keep that family at the same subsistence level would require paying 960% more for that 40 hours.) And they survived. In fact, they thrived, as did all of society when they were forced to do that. But, the type of people who created that situation in the first place are still being born. They're still running companies. And they will still attempt to wring every valuable moment out of the lives of human beings to take for themselves. If we let them.
Yeah, that's one of the big problems with capitalism. The laws of microeconomics state that in a free market, the market will produce as many widgets as possible, using up all possible resources to do so. This isn't good for human happiness or for the environment. Who really wants to live in a world where we are buying and producing as much as possible?
I do think there are certainly problems, but I don't agree what you describe is any rational conclusion of the principles of a free market. No one wants to live in a world where all resources are consumed to make widgets. Therefore, those people will not pay to buy that many widgets if they're informed enough to understand the true price of things. Most models of capitalism have weaknesses like this surrounding the need for information to be universally and equally available for their conclusions to hold, which can produce some incentives to obscure or hide information that makes exploitation easier. The issue with modern day overwork, though, isn't a lack of information but more a change in cultural values which needs to take place. Currently, the 'work hard and you will be rewarded' mindset which was productive (and often honest) in the factory-oriented past is being misapplied in modern environments where it is both counter-productive and false. 'Salary' doesn't mean 'paid for completing the work' as it was supposed to when legally created as a category, it means nothing more than 'required to perform large quantities of unpaid work'.