There's truth in what you say about the brain being lazy. It will do the minimum work unless forced otherwise, which we should unless we want it to stay in that default state as you said yourself.
According to something I once read in a psycologhy book, there's different points of our growing and developing process, where the brain simply gets rid of all the unnecessary neuronal connections, and just keeps what seems to be fundamental (which is why the older you get, the harder it can be to learn something new)
So that's we always have to push forward on our mental boundaries and don't let them hold us back, because they will eventually will narrow more and more if we just let them be.