There are lots of reasons to be careful about altcoins just like you said, it is a perfect vessels most scammers use in stealing from unsuspecting investors. But scams and fraud is not limited cryptocurrency and altcoins alone. There are many cases of fraud in stock investments and we also hear of wire fraud which passes through banks which are regulated. Whether cryptocurrency projects or conventional regulated transactions, there will always be those who will want to take the advantage to scam others.
Fraud and scams are not limited to cryptocurrency.