Why are kids inquisitive?

As kids grow and have a sense of the world around them, they tend to be eager to understand the meaning of everything and events. In most cases, their primary source of information is the adults around them, usually their mom and data, hence they ask 'why' on a lot of things and events. This not only develops their intellectual skills, but also their social skills. It is worth mentioning that there could be several developmental and/or cognitive factors that affect this trait in some kids.