Every religion on the planet has any form of light while performing the religious ritual. In Hinduism diyas are lit for any prayer or religious performance. In Islam the main sacred stone in Mecca, has fire lit in front  which is called  the 'noor' and has been lit for ever for many many years. In Christianity the candle is commonly used in worship both for decoration and ambiance, and as a symbol that represents the 'light of God'. Buddhism has candles and incense sticks lit every time for every ritual. Similarly the Jewish synagogues each have their eternal lamp. Pick any faith or religion, everywhere light carries a significant role. 

Mainly because all the religions believe light represents God. All the religious scriptures mention that too. In bhagavad gita God says that I am the highest of the high. I am never born nor do I die. I am absolute Knowledge, I am absolute purity, I am eternal light.  I am Infinite. I am omnipotent. I am an energy in the form of light. A very subtle point of light.    

 Now why just a point of light? 

God further explains that a point is infinite, has no dimensions, no measurements. Point is indestructible and so am I.