Question: Why is the brain constantly learning and searching for better ways of doing things?
Answer: Because the intelligent biological molecules at the base of our physical being are doing the same thing.
The difference is that the brain, having the combined processing power of myriad molecules and neurons, does it at stupendous speed. They do it over the aeons, constantly perfecting cells, organs and organisms.
So they have two functions. In real time they process real-time matters, the low-level processing without which we cannot function. In aeon-time they process better organisms.