I honestly find it worrying that someone would think it's some sort of deeply ingrained human trait when it's clearly not culturally universal (eg. small hunter-gatherer tribes wouldn't exist otherwise) and not present through all of history.

I think "growth" is a strong signal for people to put faith and trust into something. And that these emotions have influenced our behaviour for a long time.

Why did the Roman empire keep expanding? What made them want more? I'm not a historian nor an anthropologist (far from either!). But this feels like "line go up" behaviour. What would it mean for those in power to communicate that some part of the empire was receding? Even if, overall, the empire was objectivetly huge relative to other organised groups?

One thing I think about is there could be eroding confidence and trust of those in power by colleagues and the general population. If people lose faith, the powerful lose power; they lose ability to influence behaviour. Growth is obsessed over because it's a means to capture influence over the means of production (and capture profit).

The line has to go up because the current economic system demands it has to go up

What about outside of economics? Even metrics on https://fedidb.org: shrinking numbers are coloured red. Growing numbers green. Green = good, red = bad.

Another thought. The other day I was at a cricket match. Grand final. Because the home team was losing, the stadium started to empty. It wasn't about enjoying the individual balls/plays. Supporters were not satisfied with coming second (an amazing achievement, much "profit"!), it needed to be more.

To stretch this shitty metaphor further, when the supporters (investors?) lost confidence in their ability to deliver more, they just abandoned the entire match (enterprise?) altogether!

Again: I'm not stating anything here as fact. I'm just absolutely dumbfounded as to why "line go up" is, as you say, such an obsession. I hear you when you say that it's a consequence of how the modern economy works. That makes sense. I guess I wonder what would happen if we snapped our fingers and we could start again. I wonder what the economy system would look like. Would we still be obsessed with growth?