Well butty, I think the current "wisdom" is that there's less fat in them therefore they are healthier, or rather they come into the healthier food bracket. I just don't agree that less fat in food necessarily means healthier. It depends on the rest of your diet, for instance, where you live, and other things. Think of the usual ranges of the eskimo peoples and what's available to them and the fact that they love blubber, with good reason, and the fact that they survived in that unpromising environment because of their high fat diet, not in spite of it.
Also, the low fat stuff has been preached for quite a while now and yet the diseases a low fat diet is supposed to help don't seem to be going away. The death rate from heart disease is fallng, as I understand, but that's largely because of improved treatment rather than a fall in the rate of disease incidence. However, I do wonder if the fat content of the diets of people who avoid animal fats is really lower than, say, mine (I don't avoid animal fats) or if they've just replaced the animal fats with vegetable fats.
Do yogurt and creme fraiche often have sugar in them too? I don't eat much of either, though am happy to if they are put in front of me. Cream doesn't have sugar, as such, in it, though of course we do break down some of the fat into sugars. I don't eat much cream either, as it happens, but I don't avoid it and if I use some in a recipe and there's some left, then I use it up in my coffee or something else. Likewise with yogurt or creme fraiche, but if a recipe specifies cream, then I'll use cream and not a substitute.