I understand that those types of threads should probably be locked as the only reasonable reply to these threads is insubstantial content, see here.

I think that something similar to this could be enforced more strictly and across all sections.

I am not sure about this. There are many people that come here to earn money who have contributed both to the economy and the community. Many people that come here to earn money do not necessarily only participate in signature campaigns, as some people come here to start/run some kind of business.