A "flambe" generally involves igniting the liquor. Which burns away the vast majority of it. I referenced that with slow cooking a pork shoulder as that is a pretty common method since it is a short cut to a "smokey" flavor and gives an opportunity for the good (if a bit harsh) flavors of a whiskey to mingle with everything else in the pot.

And in the case of pudding/ice cream/whatever toppings: The point is the taste of the booze. Not the taste of the rest of the dish. Hence "delicate meals". Also, you'll notice that your "favorite" example is a dessert. As in, the thing you eat after the rest of the meal is done. Rum soaked biscuits as an appetizer is more the kind of thing that a mediocre restaurant will do to make you not complain about the mediocre five course meal and so forth.

As for marinades: Really depends on the kind of meat and the kind of cooking. Something that has time for the alcohol to cook off, sure. Although I personally think that means you aren't confident in the rest of your dish since the actual "flavor" components of most liquors are still pretty strong on their own. But for some chicken breasts people are going to throw on the grill? Might as well serve it with cigars.