Several possible explanations come to mind.

1. The original Olympic games of Ancient Greece had no comparable sports in them, so the millennia-long tradition does not apply.
2. The sports in the Summer Olympics are much more popular as participant sports in general (e.g. many more people play soccer and/or basketball, run, swim, etc. than is the case for speed-skating, ski-jumping, etc.).
3. There are active leagues in many of the sports included in the Summer Olympics, and not so much for the Winter Olympics.

The announcer just said that of the 36 countries, only 6 have won gold medals. And most of the medals, period, have been won by Norway.

In my family, we tend to watch the Winter Olympics more than the Summer Olympics. Part of it is we live far enough north that as kids we could also ice skate, ski, and do other winter sports without having to pay a lot of money to do so. I think the other reason is that during the summer, we had other things to do in the evenings and wanted to be outside; whereas during the winter, with early sunsets and plenty of snow days, we had time to watch it.

I guess it depends on where you live and what you're interests are. I don't really think it's apt to say that "Nobody seems to care about the Winter Olympics nearly as much as summer Olympics," since I'm certain that it many northern countries, the Winter Olympics are a bigger deal than the summer games.

For example, I live in Canada, and personally participate in more sports that are featured in the Winter Olympics than the summer games, so I find the winter Olympics much more fascinating. It seems as though there are more Canadian athletes (at least those that are highly ranked and have a good chance of winning medals) competing in winter than summer. I would imagine that this is likely the case in other similar nations with a cooler climate and long winters, such as Norway, Sweden, Russia, and the like.

My interest in the winter games may also stem from the fact that I have been lucky enough to live in, or at least very close to, two cities that have hosted them in my lifetime.

So...I think interest in the games depends on proximity and individual interest.

The Winter Olympics seem like they're mostly for rich white people, and certainly you don't see as many non-Whites, save the Asian nations, as you do during the Summer. And I've always associated power and athletics with events like track and field and Gymnastics.
The Winter Olympics has events like mogul, curling, and some weird cross country thing where they shoot targets. I haven't seen any winter events, even in last olympics, where I would be in awe like Usain Bolt's amazing record breaking performance in Beijing or Phelps road to destiny, also at the same olympics.
So, because I've always associated the Winter olympics with the rich and the not so athletic, I have a hard time getting excited as much as I am for the Summer.