Such bounty campaigns with payment in BTC are very few and only users with a high rank can take part there. and the number of participants is always limited.
Because the payment is in BTC, so there are a budget for it, that's why number of participants is always limited and also because no one will be able to pay for all those who are join with good income, so the participants are always limited.
For gaming platform and active promotion is necessary and it is necessary to have a budget for promotion to attract a lot of users to the platform.