It's just that ice cream is so much more creamy and delicious than it's soy counterparts. Besides, Tofulatti and Tofutti-Fruity are so much harder to find and more expensive than regular ice cream.
That's one thing I've never understood: why soy milk is more expensive than cow's milk. There are more steps required to make cow's milk than soy milk, and much more land is needed.
Example: To make cow's milk you need:
1) Cows.
2) A farmer.
3) A bull to get the cows pregnant.
4) Land for food for the cows.
5) A milking machine.
6) A pasturizer and workers to process the milk.
To make soy milk:
1) A soy field.
2) Farmers to harvest the soy
3) A soy refining plant.
Plus, there's no animal cruelty involved, and a large number of lactose intolerant and vegetarian/vegan people can enjoy a dairy-like product. It has a large enough market and is easy and relatively ethical to make (unless you have slave labour on the soy plantation), so why isn't it cheaper?