Like others have said, the purpose is to make money to enjoy the other 1/3.
Bear in mind that different people will find meaning in different ways. If you find meaning in participating in the rat race, then by all means go for it.
For me personally, I thought I _had_ to participate in the rat race, but this was a lie.
I saw this scenario play out at my last corporate job:
At that company it was typical for some managers to over-promise on what they can deliver to customers, knowing full well that their developers and QAs would have to work serious overtime to achieve those goals.
Even mentioned before the project started and the first line of code was written they would say something along the line of "this is a very important project. We're going to need you to put in lots of overtime for this".
The developers who were _idealists_ would then overexert themselves: Work until midnight, always be tired and miss out on quality time with friends family. They thought they would get rewarded when promotions are doled out, where in actual fact they were being exploited by the managers.
The managers in the meantime wasn't that concerned with the project or the goals of the company per se. Rather they were concerned with looking good in front of their managers. They were playing the _real game_.
There was always some form of emotional manipulation, like "the team depends on you". When you're an idealist you don't recognize it.
One of the developers had been with the company for 30 years, yet he didn't have a senior position, precisely because he was a pragmatist. He did his work during the day, but never did overtime. Then in the evenings he would go home to his family. Over weekends he would work on his photography hobby. He seemed a lot happier than all the others rushing around.
A younger version of me might've accused him of having a poor work ethic, but older me sees his point.