It's not that bounty hunters don't make profits out of these coins, yes they all ended very badly but as a bounty hunter you have to be smart, these coins don't have the potential that can make you want to hold on to them, it's better to sell while you can, you list Airwallet as scam but a friend of mine make 700$ from the bounty, those who hold got rekt
If we calculated the internet, electricity bill and the time spent by bounty hunters i can tell you that what bounty participants earn from most of listed project are just like faucets payment.
Nevertheless, i agreed with what you said about people to sell early than holding but i dont see a way a bounty hunters can be smart than scam project team when the project team were honest from the beginning.