Consider this scenario.

A few users, powerful users use their influence to change the forum dynamics.
We see now where we have a merit system where it is set up that these powerful members decide who decides to rank up, particularly considering that these powerful users are awarded merit points out of thin air for nothing. I think you call them merit sources. Besides from merit sources, these powerful members constantly virtue signal by meriting each other for every half-arsed thread posted in  meta (or anywhere where they see each other post really). We now have a forum where only these powerful people and people who they like rank up.

When we take a look at high-ranked accounts that earn money from signature campaigns, there is a downward trend. The fact is that owners of these accounts sometimes leave the forum, or even die. Accounts may get banned or given negative trust for some reason. What happens here is that you have less high ranking members every day because people are leaving and because of how the powerful members I mentioned before operate, very few members rank up to take the positions of those gone.

The trouble starts when we realize that those high-ranked accounts are used to enter signature campaigns to make money.

To look everything over, these powerful members control the ranking system. A system where they themselves and people who they like rank up. Other high ranking members are eliminated from the scenario for reasons mentioned above.At the end of the day, we have only these high powerful members and their friends in the higher ranks of the forum. What happens is that only this select group are able to make any sort of money from their accounts.
It gets worse, these powerful members also run the campaigns. They are paid to pay their friends and people who they like. Because of the ever declining number of high ranking accounts, these campaigns in time will pay more as demand stays the same but supply decreases. This leads to campaign managers and campaign participants (Powerful members and people they like fall into both categories) being paid more.

Now all we see are people virtue signalling these powerful members (basically sucking their dicks digitally) to get on their good side and maybe have some merit sent their way.

Signatures should be banned on the forum, if companies are serious then they can bid for banner spots on the forum. This, unlike signature campaigns, will directly contribute to the development of the forum.