Sadly, there will always be scammers because like you said "people on greedy."
The work that the users listed above and many others do it key in filtering it out, being when you have a decentralized platform there is no "authority" to protect the individuals as a whole. The community itself needs to protect each other.
Good point, I agree with you. All members of steemit community should be at alert against scammers and spammers.