We can say it is an exercise of the mind or a thanks explaining way to the god.
The soul the atma the life have proved the presence of the god every where or in science look you can say there is a certain law running in the life!
The karmakand-the puja-yagna-prayer etc. are came out from the kalpa shastra.
The god is every where so the power no body can ignore.and thus the 33 cror millions of way explaining the power are devatas. Most of the people using the word the bhagavan or the god for all is creating a great confusion in the mind of the young generation. Remember the devatas indra,Vishnu,laxmi,rudra etc.all are the power of the god.so the parmatma-ishvar-allah –god are the words stands for the same.all the temples are belongs to the parmatma.we can experience the ishvar the god allah but can not totally explain! says upanishada too! The puja we do through the devata name.The power of the god we can see and explain too.So the way of worship-prayer etc begin here. The total universal body is a great idol to prey, this parmatma tava is.So automatically the three parts gram mandir,gruh mandir and the deha mandir.these three temples.
The nature is a shakti-the power.the element fire-agni tatva.are in the form of fire-devi-mataji etc.this is a shakti-energy.