they are allocating more tokens on social media campaigns because so many participants join, even you won't find big allocation to signatures, manager just wants to do justice to all campaign participants, even though it looks unfair to signature participants
We must understand that the market has changed and as such those campaigns have changed as well, a few years ago the market of cryptocurrencies was many times smaller than its current size so the strongest community that you could find to promote your projects was this forum, so the developers gave a greater weight to the signature campaigns in this forum, but now there are a lot of more people using social media trying to find information about cryptocurrencies and as such social media campaigns have become more popular and receive most of the rewards.
Yeah, social media campaigns are more compared to signature or other passive level promotions. Better to check the solid project's bounty campaigns and stick to it rather than wasting time&enerjy on useless bounty campaigns.