Celebrate special ocassion, remembering and thanking higher engries, which are helping us susatin this life on earth and help us go achive material and spiritual growth. See how abundant this nature is, for an anology, The average adult at rest inhales and exhales something like 7 or 8 liters (about one-fourth of a cubic foot) of air per minute. That totals something like 11,000 liters of air (388 cubic feet) in a day. Now for the same in hospital they charge many thousands. All havan/homa/puja has a ritual thanking Pancha Bhoota (Earth, Water, Fire, Space, Air), The controller and Gana Devatas etc., its a subtle science.
Celebrating this way is a gesture to thank all the higher energies, and acknowledge their contribution in our lives, also reminds us not to over use and respect them.
Bhagavad Gita Chapter 18 TEXT 5
na tyajyam karyam eva tat
yajno danam tapas caiva
Meaning: Yajna/Havan/sacrifice, charity and penance are not to be given up but should be performed. Indeed, sacrifice, charity and penance purify even the great souls.