The trouble is, the designer and installer rarely have any idea how the kitchen will be used. For that matter, often the customer has no idea how the kitchen will end up being used.
There are days when I'd like to smack the genius who decided my kitchen only needed 2 circuits -- one for the refrigerator, microwave, lights, and half of the countertop; and the other for the rest of the counter, the dining room lights and receptacles, the back porch light, and the backyard receptacles. :rant: It's usually okay, as long as I don't use any other cooking appliances on the same circuit as the microwave. But it's a pain. Unfortunately, it would be more of a pain to provide a new branch circuit for just the microwave (which it ought to have anyway, given that its rated input power is 1650W). Maybe someday... but probably not.