Same goes for the Nigerian scammers who go off piste by pretending to be a little old Scottish lady with an expensive item to sell via PayPal but ruin their probably much higher hit rate by using their obviously Nigerian male personal email address for correspondence and not writing English in the manner of a little old Scottish lady. Being able to scam people by actually acknowledging their Nigerian origin is as much down to lacking the ability to pretend to be non-Nigerian as selecting for a more gullible audience (It's not like sending initial carbon-copy responses asking for deposits/money-transfer fees or bribes is especially time consuming, or like there isn't a huge number of somewhat-less-naive people willing and able to send a competent scammer a "deposit" for an imaginary good or service if they have access to accounts on reputable online payment systems)
There's a danger in attributing to counter-intuitive interpetation of statistics what can adequately be explained by ignorance and impotence.