You are right. They don't try because that is part of the strategy. They realize that 90% of the guys out there are going to spot their mistakes and move on. The other 10% who, either do not see or are too stupid to recognize, the fake. are their customer base. Those are the guys who they know they can get to send an e-transfer or whatever else they have planned.
We've all gotten those letters or emails form some Nigerian Prince's lawyer who needs your help getting his $50 Million dollars out of the country. They are often full of spelling and grammatical errors. Not what you would expect form an educated person. They do this on purpose. The psychology is that if a person is willing to overlook those kind of obvious warning signs, they are more likely to fall for the scam.
Same applies to all of these obviously fake ads.
Cheers
J