There are couple of good reasons:
Quite a lot of progress comes from the mindset "I don't want to do this stupid, hard, boring, tedious task. In fact, I want to sleep on my couch all day long. How can I achieve that?".
So the person starts thinking, trying out solutions, and eventually makes everything better automated, more efficient, etc. Eventually, more people adopt the solution, and it becomes a norm.
And once it becomes a norm, it also becomes a stupid, hard, boring, tedious task for the next generations.
Consider washing dishes. It was considered stupid, hard, boring, tedious task, until someone invented automatic dishwasher. How marvellous it is for the people, who, for the fist time in their lives, are liberated from washing by hand! And then, for their kids, it becomes a stupid, hard, boring, tedious task to load and unload the machine.
Such is a circle of life.
Assuming world, where people are not power hungry and selfish, and where war and conflicts aren't a norm, it would make less sense to be attracted to live impression of Conan The Barbarian, and more to the smart guy who can improve your life in thousand little ways (see my first point).
Surely, it wouldn't always work, but then again there are notable exceptions in out world as well.
Protection from Mother Nature's wrath
Even if other people are not a threat, there are still tornadoes, earthquakes, malaria, locusts, and whatever lives in Australia. One way or another we would have to protect ourselves from all those dangers, or at least try to mitigate their effects.
Sense of adventure
What is on the other side of that lake? I won't find out until I learn how to build a boat.
What is on the other side of that sea? I won't find out until I improve my boat.
What is on the other side of that mountain? I won't find out without proper gear.
There is always more, there is always something beyond the horizon, there is always something we want to explore. But to find out what's on the dark side of the moon you need to constantly improve your technology.