For a finite-size system to persist in time (to live), it must evolve in such a way that it provides easier access to the imposed currents that flow through it.
The first fact about the celebration of a birthday is that it is a way of affirming defiantly, and even flamboyantly, that it is a good thing to be alive.
It's very dangerous to mix up the words natural and habitual. We have been trained to be quite habitual at communicating in ways that are quite unnatural.