A signature campaign is organized by company who want to promote/advertise their services, but they pay good to their campaigners.
If you have Time, knowledge about bitcoins and have mobile or PC you can earn money from this.
This thing will never end until demand and supply for bitcoins are there.
Though mass information is available about bitcoin on internet, people still believe in bitcoin signature forum.
Here the share or ask their questions, get solved their quarries.
This helps in advertising bitcoin indirectly.
Also signature campaign companies are getting good income from this activity.
So why one would close signature campaing.