I can kind of see it this way. Anyone remember that episode of Arthur where they're depressed and bored and realize they need a holiday? Well, that. All that. Even a die hard winter fan gets the blahs when January slowly turns into the actually worse weather February. Christmas is a big freaking deal, and as an adult I realize it's not just Christmas Day that makes the day special, it's the anticipation. The preparation. You have this nice long build up of watching TV specials, listening to music (even if you don't really enjoy it, it's still nice background noise), and the candy and food and stuff. Then New Years Day happens and nothing. Nothing for a whole month. Then the Valentines prep pops up. It's not the best thing to get excited about, but it's something.
Plus, there's always that little nagging bit of nostalgia. I mean, remember when you were in Elementary school and you got those cheap little cardboard multipack cards? You'd send them, you'd get them. That's a nice little memory, especially if you're sentimental enough to keep them (and I totally wish I did). I think the problem is the romantic angle, but like I said, if you're lonely, it's not going to be for this one day. So why fret over one day? Plus the candy may not be half as good as the following holiday (I can't stress enough how much I love Easter candy), but candy's candy. And it's on sale the day after.