Running a bounty can't be cheap. For every person participating you have to pay a fee. For telegram and airdrops, how do the devs afford it?
Since you are talking about alt coins, i can very well tell that the tokens the owners are providing are cheap because the valuation comes from the amount they say. I have not seen any airdrops or bounty payments in bitcoin which is the real value and if any team is doing that, then you can trust them as they are putting real money to conduct these bounties. I have seen some bounties paying in bitcoin but majority of the bounty campaigns are paid through their coins which has zero valuation.