The argument could be made that giving as much of yourself as possible is a crucial ingredient to making the startup worth it. After all if you are holding back the product and business isn't building itself.
Of course it probably isn't healthy to make a business the center of your life, but people who do will likely have a higher chance of success in that business because they are willing to put forth a lot more effort to keep it going than someone who isn't as committed, and therefore not as concerned if the business fails.
Are you really being outcompeted if the startup winds up going basically nowhere and you've put a year or two of huge time and opportunity costs into a failure? What if startups weren't worth it unless they were well-run enough to require very few hours over 40 from its employees?
It's a falsehood that appears intuitively obvious. Working stupid hours destroys not only your productivity and personal life but also your judgment, to the extent that you lose the ability to judge your degree of cognitive impairment. It's like coming into work blind drunk: not only are you a liability to yourself and others but you don't realize how much of a liability you are. You may well end up being outcompeted by someone who put in forty hours a week of smart, correctly applied work.
Of course it probably isn't healthy to make a business the center of your life, but people who do will likely have a higher chance of success in that business because they are willing to put forth a lot more effort to keep it going than someone who isn't as committed, and therefore not as concerned if the business fails.