Santa should get with the times and say “LOL”.
Dunno about Santa, but I know why The Flinstones go “Yabba Dabba Doo”
Would you rather he said No,No,No? 
The guy gets out one a year, and it’s supposedly spent giving gifts to children all over the world. That takes time.
Folks, I ask you. I you had just one night a year to get out on your own, and you had most of that night taken up by giving away presents, wouldn’t you cut the small talk and ask for what you want for fun?
Ho! Ho! Ho!
Of course, you meant capeesh, right?
He doesn’t say HO HO HO at all.
The traditional image of Santa on the rooftops is taken from a fifteenth century wood cut which can be be found in the [Santinomicon](you expected a real link?). Santa is on the roof, about to deliver presents to the King of Bavaria, when he is disturbed by the slithering horror of N’Claus’n’ht’oth. His reaction is to to exclaim “OH OH OH” as his beard turned instantly white. Santa became permanently insane and was doomed to an eternity of pain and suffering at the North Pole. His only escape, even to this day, is to deliver presents on the anniversary of his imprisonment. For reasons not known to mortal man, the image of the woodcut was reversed and this story was lost. Until now…
I always heard it’s because he’s only got popcorn balls.
Your version’s funnier, though.
Maybe not. It seems no one can quite agree how to spell that word in its slang usage: http://www.wordwizard.com/clubhouse/founddiscuss1.asp?Num=4408
It’s because Santa Claus is a cryptic personification of Satan.
Apart from the obvious anagram, association with demonic elves, purpose of distracting the masses from celebrating the nativity by placing attention on material pleasures, etc, “HO HO HO” is a satanic signifier.
Let him that hath understanding count the letters between “H” and “O” in the alphabet: I J K L M N
So HO HO HO represents…?
Behold, it is the number of a man.
*cue scary organ music, thunder and lightning *
OKay, I’ll ask.
So why do the Flinstones go ‘Yabba Dabba Doo’?
Because if he said **"Hi! Hi! Hi! **everyone would think he is a lush.
People would think he was Nelson Muntz.
That’s what I always say…