Rat race is just like what it sounds, rat racing in a maze for food.

It's pointless and the race never ends. winning the race just means the rat waits for the next maze/race.

When applied to human, it basically looks at life as pointless. You grow up, spend your life working, then retire. Sure, you went on vacations, met your soulmate, have kids and whatnot. But just like the cheese, its temperate. it's pointless, and at the end of the day, everything you ever done holds no purpose except prolonging your life. and come a few hundred years, everything about you is erased. The cycle of pointlessness is why we call it the rat race.