The constant need for growth isn’t about making life better for most people. It’s a structural requirement of capitalism itself because the system runs on profit which comes from the value created by workers. Companies have to constantly expand their markets to keep the rate of profit from falling, cut costs, and find new ways to generate more value from us. If the economy stops growing then investment stalls and unemployment rises because the whole financialized structure is built on the expectation of future returns. The purpose of the economy isn’t to improve our lives, and the whole growth treadmill we’re on exists because capitalism demands endless accumulation to sustain itself.

Outside of the normal Marxist reasons for capitalist pursuit of growth, there’s a resource demand argument for growth (which would exist even without capitalism).

Think of it like this: everyday, people are born or immigrate here. Everyone has needs that need to be satisfied, like food, housing, entertainment, medicine, art and culture, education, clothing, and water. Let’s imagine that growth didn’t occur. These needs would still be there, so that situation would mean that everyone would have to make do with a little less per-capita – or some people would have to go without. What other conclusion would there be if there’s no growth in production and supply but a growth in total demand?

Even in a socialist or communist system, growth would still need to be planned for because the population tends to grow and people have needs to tend for. Unless you are planning for a population to be maintained at replacement rate on a multi-generational scale, economic growth needs to happen to accommodate a growing population.

Edit: to be clear, I am not suggesting that capitalism does resource distribution well. I started out by saying “outside of the normal Marxist reasons for capitalist pursuit of growth” for a reason. I’m just saying growth needs to be planned for no matter the mode of production.