Why? Because of the advantages. I can't even participate in signature campaigns?! It's like saying to someone leaving university to start with cleaning work or sweeping streets. 
Because the signature campaign would be renting your advertising space under false pretenses. You would be pretending to be someone you are not and defrauding them. That is why people in this community would not trust you.
But I understand that trust has nothing to do with the forum rules but everything with what users think of one another. Correct? Does that also mean that there are no forum rules, no sanctions, and that it's a wild West and anarchy around here?
You seem confused, these two sentences directly contradict each other. The rules have nothing to do with trust, that is a matter for the community to police. The forum rules can be found in the stickies in this board and are enforced by the moderators. Aside from that running your monetary system is a bit anarchic I suppose.