Yes, I completely agree with your opinion on this topic. Translation campaign is more profitable than the signature camping. As well it's not an easy task to do the translation. But it is more beneficial than any other task.
Each of those bounty has their own preference on what they are going to focus with.
For those who are focused with advertising here in the forum, they are increasing the reward through signature campaign. And for those that don't see any valuable help for having signature campaign, they are increasing in some other media campaigns. In short, that depends on the bounty on where they'll focus.