I don't believe all of us are hard wired for curiosity. This is further outside my area of expertise so I can't give any citations or references, but I do recall reading about human sleep patterns having evolved to allow diversity which benefits the community but not necessarily the individual.
My paraphrasing of what I read is blocked off:
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Some people are light sleepers. Slight sounds wake them up. Some (like myself) can literally sleep through an earth quake and barely notice it. I woke up briefly for about 2 seconds when an earthquake hit where I lived (sounded like the china cabinet fell in the living room). Noticed everything seemed ok and immediately fell back asleep.
People who are light sleepers have one primary pro and on primary con, both opposites.
Pro: If a dangerous situation presents itself, they will wake up and be aware of it very easily.
Con: Lack of sleep due to heightened alertness.
Heavy sleepers:
Pro: Will be fully rested every day assuming they stick to a regular sleep schedule, unhindereed by stimuli which are not a thread.
Con: Should a stimuli that is a threat present itself, they are less likely to become aware of it until it's potentially too late.
In primitive societies with a small band or tribe, this worked very synergestically. The light sleepers though less well rested compared to heavy sleepers, were always likely to become aware of a threat and respond during sleep. At the point they become aware they are able to awaken the heavy sleepers who are far more likely to be well rested and capable of handling the problem.
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Now, that was purely speculative I'm sure. Whether or not those traits and the diversity in the community coming to be due to natural selection favoring it, or just by coincidence, a logical explanation is possible.
A similar line of though could apply to the trait of being highly/extremely curious.
Low curiosity people:
Pro (Survival): Far less likely to involve themselves in activities where risk is unknown. (Eating new food, exploring new areas, attempting new physical activities "to see if you can do it" or experimenting with toxic/fatal substances).
Con (Progression): Also far less likely to make discoveries of nutritional foods or therapeutic substances, areas with more abundant resources, and discover new tools (from a hammer smacking your thumb to death by radiation damage being the dangers).
High curiosity people are far more likely to do the above.
Let's face it, there are some people who really just don't care about learning something just for the sake of learning it. I like to consider myself a polymath in training. If I don't know something, I want to know it and know how to apply it.
Other people are content just following the instructions of others on what's safe and what's not.
Everyone here, most likely falls into the set of high curiosity people. We don't understand why someone wouldn't want to know what it's like to try , or may even consider it impossible that they don't and that they have just fallen for prohibition related misinformation.
There was a study (believe I saw it on the History channel in a series about our evolutionary history), that actually showed that intuition and willingness to experiment (probably very closely related to curiosity when attempting a new idea) is not even a trait children, but is of adult monkeys (chimps I believe).
A specially designed box with a stick a nob and some holes, or some other similar puzzle type scenario was created, one opaque and one clear.
The opaque one was used first to train the children and the monkeys how to get a piece of food from one of the holes. The taught them to do a "ritual" of sorts. My example is probably not the accurate ritual used, but idea should be consistant.
1. Take the stick from the top of the box.
2. Bang the box 3 times on the sie.
3. Put the stick into one of the holes and turn it.
4. Put the stick into another one of the holes and out comes a piece of food.
After the children and monkeys mastered the process, they then exchanged the opaque box with a transparent box. The children continued to perform the ritual in I believe all cases. Their intuition and curiosity to try a new "ritual" was non-existant. The monkeys however, seeing the food, performed Step 1 and Step 4, obtaining the food without the extraneous effot required.
The hypothesis is that we as a species evolved with an inhibited desire to "try something new" even when confronted with evidence that it might work.
The outliers in our species at that age would be the ones who got the bright idea that all the monkeys were able to figure out easily.
There were other interesting facts in the differences in evolution between humans and monkeys as well. One being they have on average an eidetic short term memory. Once trained to hit a sequence of randomly placed circles (numbered 1 through X), they then were trained to do it when all the numbers were only visible for up to a fraction of a second. They still were able to hit all the buttons in the correct order, despite the label being missing, majority of the time.
Humans still have difficulty when 9 buttons are up for 5 seconds... monkeys no problem at a fraction of a second.
It's really interesting to see the divergent evolutionary paths between us and our cousins in the Hominini classification (Humans, Chimpanzees, and Bonobos), and still very interesting just in primate classification.
All in all... the answer of why? Because our species has evolved to have a diversity in the range of curiosity, to explore, to test new ideas, and learn about our surroundings. Due to that diversity, a set of the population will find the topics that interest them most and pursue them with a level of curiosity and desire to learn not typically associated with the majority of our species.
Those with an interest in astronomy and space, why did they have the desire to prove earth revolved around the sun, or physically go to the moon?
Those with an interest in mechanical engineering and combustion, why do they have a desire to build faster, more efficent and more reliable engines?
Those with an interest in the human mind, or the spiritual facets of our existence... their desire for "expanded consciousness" likes in the same explanation.
Some of us are just wired to "want to know". Whether genetically or learned behavior, who knows, but the genetics definitely allow it.
If you want to go past "curiosity", you could say we evolved to desire it.
If you want to get into the why we exist to begin with... good luck.
