ICO - initial coin offering is the best way to sell and distribute new altcoins to the public and start the circulation when it bumped on coin exchanges.
there are a lot of ICOs running today but only few of them will succeed because the ICO competition today are very tight and most of the failed ICOs will just vanish or some of them will be tagged as scam and fraud.
That's why bounty campaign participants are helping them to promote and advertise in order to attract new investors and supporters.