I think this has something to do with the number of people involved, because most Facebook and Twitter don't limit the number of participants!
yes that right my friend , now to much participants joined for socmed bounty like facebook and twitter i see in every bounty more than 2K participants! , and maybe other people using multi account too.
Most are using multiple facebook accounts and twitter. In 2017 when I joined only 300-400 people joined twitter and facebook but now each campaign has 3000-4000 participants. A huge amount of accounts and it makes the true bounty hunters poorer