RE: Why is cake so rare in restaurants?
I have to disagree.
The underlying chemical taste of any "mix" cake is, at least to me, unmistakeable.
Pies can be difficult. Pastries? I'm unsure what that includes, but unless you're doing elaborate petits fours I'd say they're do-able.
Custards are every chef's dream: extremely easy to make, with an almost invisible food cost, and appeal across a wide range of cultural and ethnic tastes.
During the great creme brulee excitement, years ago, I never failed to marvel at how much I could get away with charging for a couple of yolks and a few ounces of cream.
Cakes are tougher. Many more variables in a cake batter, and much more sensitive to variations in oven temperature. This is a big factor, especially in smaller restaurants where the pastry chef shares ovens with the line cooks and it's hard to get an even, consistent heat.
Personally, I still cherish my mother's devil's food cake, made with raspberry preserves or, if she was feeling whimsical, pineapple preserves, between the layers. I'm getting weak just thinking about a huge slice of that with some ice-cold milk.