My thoughts is that these signature campaign is obsolete in todays social media world. They can spam telegram, Facebook, email accounts, twitter etc to promote their ICO/airdrop/Bounties.
This forums would be better off with focused discussion on real issues, ideas, Anns etc. People can still earn their bounties in the other arenas. Bitcointalk has been diluted to a point of ridicule. I wholeheartedly agree with OP, but unfortunately I do not have any merit to prove this.
I don't know, do you really know what is a signature campaign? Do you think that it would be good if promoting ICO is prohibited here in the forum. Let me tell you mate this not only for all smart philosophers or battle of the brains ( as I observed ), its all about business. why do you think mods created a bounties section for altcoins? They also have benefits even you, I admit even me. Some of big investors are here on this forum, so represent a signature here in this forum is more better.