of course, he arose in the 1800's when kids started being treated like kids instead of adults. and when christmas turned from a lower class rejection of the rich into a family holiday...
i think he exists so that when poor people and kids took a long hard look at the cold winter coming up - with fear and foreboding - they needed someone to assure them that they would survive - rich adults wouldn't eat them or leave them hungry and homeless. they needed inspiration and encouragement. so santa comes a long and tell them:
"look at me - i am FAT - you will not starve!"
"i am old - and yet healthy and happy! you will have a good future!"
"I am jolly - and yet not drunk, and i won't beat you like your boss or dad!"
"I am dressed in blazing white and burning red - i have warm red cheeks! you will not freeze!"
"and we will be divine and vital!"
"i am so rich i'm just giving all these toys away - we DEFY winter's poverty and meaness!"
"i am big and STRONG, but sweet as pie! you don't have to be a jerk when you grow up!"
"i can FLY! - what more do you want?!"
"and yet you leave me cookies - to feed your own magical dream..."