Technically there is no difference between performing a scam on ethereum or on neo.

Ethereum has gained a lot of attention in the last year. This has attracted a lot of small legit companys, developer, so-called 'investors' and, of course, scammer.
The reason that most scammers choose to perform it on ethereum over neo is because ethereum offers a bigger audience (and therefore more people to steal money from).
Why would they using neo to scam people if they could make much more money on ethereum?