Sorry, android209. Your reasonable question is getting caught up in a muddle of minutiae.
Your question was, “Why should local/national calls be differently priced?”
The short answer, of course, is that LD companies gotta make a buck, too! 
The big answer is that in addition to recouping the marginal cost of carrying your minute of traffic across this great land of ours, LD companies have to recoup a fair return on the massive capital they have invested in building the network in the first place. So even though the additional cost of carrying your minute is quite low (not quite a billionth of a cent, but under one cent), charging a price that low would leave no incentive for carriers to invest a few billion per year in upkeep and expansion of the network. So the network would die, and we’d all be stuck with tin cans and string.
Additionally, the marginal cost to a LD carrier is actually far above one cent per minute of carried traffic. (What? He just said it was below that. What an idiot!) OK, their cost to carry it from Chicago to NY is under $.01, but their cost to carry it from their office in Chicago to your house runs about 2 cents, and their cost to carry it from their NY office to my house is another 2 cents or so. These are access fees, charged to LD companies by local providers such as Bell Atlantic and Ameritech. These fees have been coming down pretty steadily since 1996, and are expected to fall further still. So there is a source for future decreases in LD rates. As I alluded to in an earlier post, in the future it is not unlikely that large users will see the same rates for local as for LD if they agree to bundle the products with one carrier. Us little guys will probably see at least some extra charge for LD, since individually none of us generates enough minutes to make carriers’ networks hum.
Your other question was about last incoming call service. That’s a little more craven. You have to remember that the UK service historically has been more heavily metered. That is to say, lower line charges and higher per call and per minute charges. So that extra call you make in the UK can mean serious money to British Telecom. Here in the States, not so much. Most places are either not metered for local at all, metered at a “per call” rate, or lightly metered. So the revenue curve works better if you can charge $.75 for each person who wants the number than if everybody got it for free. There are also regulatory issues involved, but no need to go into them here. Most competitive local telcom companies, if you have access to such a thing, will in fact throw the service in for free.
Livin’ on Tums, Vitamin E and Rogaine