Resources are scarce.
So spiders have developed the toughest fibre material to spin their webs because that makes little saliva to spin a big net and eat many flies.
Plants turn their leaves towards the sun to catch the most light per leave.
We discuss with friends to find the fastest way to drive to the office and we weigh kilometres (liters of petrol) against time spent. We are economical in most of our doings. Even when we do something ‘stupid’ like buying Gucci instead of Zara or helping a friend, there is a benefit in terms of status or friendship that may eventually pay off. Economical behaviour is about all resources, not only money.
All species try to accumulate wealth to survive a bad period. This is the capitalist principal. So your cat eats all it finds in its bowl for inborn fear that the next meal may be too far away. Bees collect all the nectar they can find to build nests, feed the queen and the next generation. They gather surplus and invest in the future.
All animals test potential partners for optimum fitness for procreation before they have sex. Humans do the same. It makes economic sense to be with the fittest as this increases chances for offspring to survive.
The economic principal of maximizing reward while minimizing effort is ubiquitous, in nature and in humans. The economic principal reins our entire behaviour. Growth is the imperative.