Why do People cut cake and blow out candles on birthday? What is the historical or cultural significance behind this tradition?

In his tweet Amitabh Bachhan liile bit surprised to celebrate practices of Birthday celebration he wrote so many questions regarding this

“ Englishman Happy Birthday left a practice and we are still its slave!  Why A cake? Why A candle? Why we blow candles? Lamp ignition is in our civilization”.

Although the exact origin and importance of the candles and the blowing practice is unknown, there are multiple theories to explain this custom.

Greek theory

The tradition of placing candles on birthday cakes is said to be attributed to early Greeks to honor the goddess's birth on the sixth day of every lunar month.

However, the link between her presidency over fertility and the birthday customs of candles on cakes has not been recognized.

Pagan theory

The use of fire in ritual practice is very old. "Birthday candles, in folk belief, are endowed with special magic for granting wishes. . . . Lighted tapers [candles] and sacrificial fires have had a special mystic significance ever since man first set up altars to his gods. The birthday candles are thus an honor and tribute to the birthday child and bring good fortune. . . . " according to Qura .

German theory

There is evidence of the use of candles on cakes at birthday celebrations in 18th Century Germany. This version of the tradition can be traced to children for a birthday celebration.

Big B also shared a poem of late Shri Harivansh rai bachchan urging to celebrate birthdays and must hymn this.

वर्ष नव,

हर्ष नव,

जीवन उत्कर्ष नव।

नव उमंग,

नव तरंग,

जीवन का नव प्रसंग।

नवल चाह,

नवल राह,

जीवन का नव प्रवाह।

गीत नवल,

प्रीत नवल,

जीवन की रीति नवल,

जीवन की नीति नवल,

जीवन की जीत नवल!