Partially because in order to always learn new ideas and adapt to constant change, the brain never "finishes" - sort of like when you burn a cd or dvd, and make it multi-session in case you need to add a couple of files later. At no time are you truly sure that you have found your place and the truth of life, it all keeps on going and changing.
So is there truly no end in sight? Do we know enough to say that there will always be something more to know?
A simply case in point is the stats in the latest issue of Wired on neutrinos:
- Estimated number of neutrinos detected: 725,000
- Rate at which solar neutrinos reach Earth: 60 billion per square centimeter per second
Maybe some day we will know and understand enough to be content, to fill our days in peaceful contemplation with no need to adapt to change - but for now, there are enough changes and challenges ahead to make it wise to be immature