But that is outweighed by distinct advantages - including the total anonymity of the scammers, lack of intervention measures, and capturing those who are most likely to fall for something that isn't what it seems (ie. bitcoiners).
Western Union is mostly used by immigrants sending money back to their families. Gift cards are... gift cards! People don't expect to get anything in return. Also they are not normally used for large sums of money. But Western Union is a well-known scamming vector, and they keep their customers informed about it.
Fraud Awareness with Western Union US
Bitcoin? The warnings are brushed off by coiners who accuse us of being shills for fiat banking.