Apparently these scams have been operating for well on 2+ decades now (originally through the mail.) Nigeria has its hands full with these things, and has set up task forces to deal with them. Unfortunately, these scam artists give the entire country a very bad reputation -- and that is most definately a concern for the Nigerian government.
I can't believe you actually got one of those things

It's been such a heavily utilized system, and yet I've never received even one

When do I get a shot at my millions? Hehe. I like how the lawyer used the term GHASTLY to describe the accident. Who the hell uses that term in a "professional" letter?