Why is there no vegan "diet" food??

Well, I have just begun my journey into veganism, and while I am finding plenty to eat, I am really disappointed that there are no replacements for my favourite dairy/egg dieting staples.  I know this is because "diet" food are usually chemical-laden and don't fit in with the whole vegan-clean-eating-whole-foods thing...but DARN IT, I like them and I miss them!

Can anyone help me find or make vegan replacements for the follwing things that have roughly the same calories?

butter spray

fat free mayo

fat free sour cream

yogurt (soy yogurt has twice as many calories as dairy??  why?)

Skinny cow ice cream sandwiches (tofutti cuties are like half the size and have 50 more calories??!?!) or any low-sugar, low-fat ice cream-like thing.

(ETA: for the sake of clarity, I have changed the product name from a colloquialism which has proven either confusing or gross...)

Or, if you don't have any suggestions, maybe we can just commiserate and you can share the diet foods you miss from your dairy/egg/meat-eating days.

At Whole Foods, they sell a canola oil spray that is butter flavored and labeled vegan.  It is made by the company Spectrum.  I usually just mist olive oil for cooking, but this canola spray is good for things like pancakes, etc.