This is good advice for a very narrow segment of creative people and not everyone at large. It's terrible advice for people with children, for example.
Of course, there's a balance to be had.
So, if you want your kids to get a proper education you'll either have to pay for a good school or get a house in a nice neighborhood; both things which require one to constantly be paying a substantial amount of money, whether it be for the mortgage, taxes, or tuition.
That said, I generally agree with the sentiment. People with commitments are less free to play with their resources, at least if they are responsible. An who wants to invest in someone who's not responsible. There are, of course, exceptions, and even times when the opposite holds true; commitments can force a level of responsibility and drive because the stakes may be higher.
The downvotes were more likely because the comment was false (pg and YC invest in plenty of founders over 35) and unduly personal ("your mindset is exactly why...").
I am tempted to see if blind devotion to pg leads to downvotes, but I doubt HN would care. :-)