Certain combinations of elements have unique physical, physiological and psychological properties and functions in nature.
The elements combined to create the three doshas (tridosha) in Ayurvedic are combined in such manner in order to create and sustain life:
Vata (air / space) = the energy of movement = the life source (breath / prana), nervous system regulation, activity and movement in the body, elimination, circulation, heart pumping, etc.
Pitta (fire / water)= the energy of transformation and conversion = digestion, assimilation, absorption, confidence to move through the world as you are
Kahpa (water / earth) = the energy of form = supports the structure of the body, builds tissues and lubricates the joints, love, compassion and empathy
We need breath, circulation, the ability to absorb our food for energy, to excrete waste, and we need our physical form to protect our vital organs and musculature to support movement. If the elements were combined differently, they might not create these vital functions in order to survive.