Some people are so gullible because they are usually too trusting of people and are also greedy and when they see a chance to get money etc then they will jump on it.
Like those scams that say that they need help moving money from one place to another and they'll give you millions of dollars.
People who think they want or will get all that money would be gullible enough to give out their bank account details etc and then they will be left with nothing.
Some people are not taught young to not trust certain people.
You should teach your kids on how to spot scams and not be trusting of everyone and everything.