Because, like anyone else, they want the sun to come back.
Fortunately the sun isn't fussy and comes back regardless of which version of the festival any particular individual celebrates. It's being doing so since before religions were invented and will no doubt continue to do so after the last one has been forgotten.
Let's not forget that Christmas really belongs to the Pagans...
Apparently, the season of good cheer did not start out as exclusively a Christian festival. According to Pagans, the early Christian church hijacked December 25 to celebrate the birth of Jesus because they saw that everyone was already having a good time and decided to take advantage of it.
Look it's near the winter solstice with minimal sunshine, crap weather and every totally depressed. It's a bright festival with lots of pretty lights everywhere and enforced jollity and dolled up wimmin- who couldn't like it (apart from the appalling music and silly religious emotion). I draw the line at going to church and have absolutely no religion, detest turkey and Christmas pudding, but it helps people cheer up and that's no bad thing! Religion is a total con, but it seems humans have a fundamental need to make up crap to believe in and take comfort from it, so I suppose it is good for them. It's just unfortunate whilst most religions celebrate peace and love, some have a fascination with death and regarding non-believers with disdain to be terminated at will. Well one actually.
In downtown chavtown today, getting last minute Xmas items - Salvation Army band playing carols against the Jehovah's Witnesses market stall facing them with a large poster saying 'AWAKE! The Truth About Chrismas' An interesting juxtaposition.
The JWs hate Xmas as a it's 'voice of Satan' with pagan origins.
"This is very similar to the suggestion put forward by the Quirmian philosopher Ventre, who said, 'Possibly the gods exist, and possibly they do not. So why not believe in them in any case? If it's all true you'll go to a lovely place when you die, and if it isn't then you've lost nothing, right?'
When he died he woke up in a circle of gods holding nasty-looking sticks and one of them said, "We're going to show you what we think of Mr. Clever Dick in these parts...'" ~Terry Pratchett, Hogfather
Huge log fire, twinkly tree, Aga cooked roast pork with sauerkraut, silly hats, leaving out a glass of port for Santa (i.e. yours truly), not going to work, nice ripe stilton, PPRuNe pals coming to visit, Brideshead Revisited on DVD and an uberbabe under the mistletoe
“What the hell are you getting so upset about?” he asked her bewilderedly in a tone of contrite amusement. “I thought you didn’t believe in God.”
“I don’t,” she sobbed, bursting violently into tears. “But the God I don’t believe in is a good God, a just God, a merciful God. He’s not the mean and stupid God you make Him out to be.” - Joseph Heller, Catch 22
Because we don't get a bloody choice since everyone else has been brainwashed into this commercialised "holiday season" nonsense and that means we HAVE to participate so our partners don't get all grumpy at the thought of there being no "Christmas".
(personally, I'd be happy to celebrate in a proper pagan manner by sacrificing a few chickens/goats/sheep and then having a proper orgy in a field somewhere, but "Christmas" is the tradition that *must* be followed. Bugger)