Ice cream is, OK not great, but surprisingly not as bad in terms of fattening as one would expect. It has a lowish glycemic index; the milk slows the sugar's absorption. So it doesn't make that blood-sugar spike which prompts your body to grab the excess sugar and store it away in fat cells. If you were trying to lose weight, probably better for you than, say, rice cakes, which are pure processed starch and hit your bloodstream nearly as fast and hard as candy.
In general, if you're going to go for desserts, rich is not as bad as sweet--lots of butter and cream won't screw you like concentrated sugar will.
Of course as
@SveNo says, weight loss isn't what they're trying for anyway.