Why yes, actually, I *do* know the "reason for the season." Several centuries after Jesus' death, early Christians co-opted several winter observances, including the Romans' Saturnalia and Sol Invictus Festival, the Celts' solstice rituals, and the Pagans' Yule, in order to find acceptance and ingratiate themselves to the local populaces they were seeking to convert, leading to today's capitalistic and materialistic celebrations that blur the line between church and state and lead the radical right to pop a vein over their non-existent self-identified discrimination.
Thanks for asking. Ho, ho, ho! :)