http://www.techworld.com.au/article/428151/why_nigerian_scammers_say_they_re_from_nigeria/

Click on the link within the article for the complete pdf research study by Microsoft if you're interested. In a nutshell, scammers want to find the ideal target (those who have money and are gullible and unaware of the standard scams that are around).   Finding this tiny percentage in the general population is expensive in terms of the scammer's resources (time and money) so the best way to find targets is for them to identify themselves.  i.e. people who do not know that scams typically originate in Nigeria; are not alerted to something fishy by the obvious signs such as outrageous stories, bad spelling, poor quality letter writing etc.  These strategies are used on purpose because educated people who spot them straight away are not the intended target of the scammers.   What scammers hate is putting in the time and effort and then have their target pull out somewhere along the line.  If you read the study you can see how it all works mathematically - it's a matter of efficiency.  They are most likely to succeed if they can locate gullible people by weeding out the smart ones first.  Can you see how it works?  It's a process of elimination.

Note the suggestions of how to get back at the scammers - by pretending to be a gullible target, waste as much of their time as possible then drop them in it a the end.  It is actually a sport.  Many of us have done this with phone scammers.  But don't do it with emails or ebay accounts because you should never make contact that way or click on links. 

You want to be in the population that gets rejected in the first round i.e. by reading all the advice given by banks and software security experts, keeping up to date with the news and websites such as scamwatch.org.au.  Forums are also a good source of information.