Although Twitter and Facebook bounty always received lower percent of stake than other part of bounty campaign but it's not the problem make you guys only earn little with these bounty. The main reason is there are so many participants in every twitter and facebook bounty cause everyone just need to spend few minutes everyday to make a twitter tweet or facebook post, few seconds to share or retweet. But with signature and other part of bounty campaign everyone has to spend hours everyday to work so why don't you spend hours a day to join other part of bounty campaign to earn more?
if he want to earn much higher in social media he need to work hard and join social media campaign that he can able to join. There are many social media campaign open that need participants just join them all, after that you will earn enoug also try other task here.