...It's not lol, it's literally not anymore effort than doing it legit, what extra effort is there to take the dudes item and currency, ignore and just keep on mapping/scamming?

Because they have to normally craft too. If somebody is going to randomly scam people, they're probably not going to patiently and thoroughly complete dozens, hundreds of trades over weeks, months, multiple leagues.

are you telling me everytime you look for services on GGG forums or ingame chat you do a background check and search reddit and the like for threads mentioning that person scamming?

Lol, if they're crafting anything worth real money fuck yes. They're never doing a mirror service without checking, they're not handing the dude several exalts without checking (exception of idiots like the one in OP's pic). They make big currency from the big crafting mods, the expenisve ones, with low amount of trades, and those are the ones that people will actually check into you for. And if nobody gives you those, then the guy is just scamming people for several chaos trades, which are high quantity low quality, so he'd already be earning plenty of tips and fees from those if he didn't scam.