i don't know exactly when i started taking coffee after meals, but i think it must have occurred when i was trying to cut down on my dessert intake.
the first time i did that wasn't exactly fortuitous, but for some reason i decided to stick with it. the next day, i added a teaspoon of sugar -- which seemed to do the trick. and so a new habit was formed.
as my new beverage of choice, it solved a couple of problems for me. aside from the cutback on my dessert bills (and the calories it shaved off from my usual intake), it also eased my fondness for soda drinks.
and as my sister never fails to remind me, hot beverages are a better choice during meals (except on hot days, of course -- that's where i draw the line).