This question was discussed a lot of times.
I doubt that all bountyhunters have so many tokens that they can drop the price, usually the bounty rewards are around 2-5% of all ICO tokens. So perhaps the main reason is the red market.
In December 2017 – January 2018 you really could see how your tokens (even shitcoins) made 10-100X after the ICO, but unfortunately today the situation is quite opposite.
According to these circumstances you can sell your tokens immediately and then after some time buy them even twice as much.