Marketing in general, that's what the main reason. People engage to use the site for obvious reason, since they have a good reputation here.

When an exchange is introduced here that is affiliated to Bestchange, people keep in mind that they might be "good" for that reason. Same reason for an affiliated exchange that has an issue or scammed someone, once reported to bestchange they make move to remove the exchange on their platform after the investigation.

This is the same for other long running campaigns, the more they promote the more their users trusted in them, the more they get users the more their sales. Well this will based on their actions too because some e.g. casino, who have campaigns here but then got an issue, after their unfair actions they got tagged/flag and tainted their reputation.