.. I was here before the merit system was introduced; you should have seen how much spam there was. Everyone could simply rank up with the only requirement of being active and posting; it didn't matter what; just post whatever comes to mind. You could even become a Hero member in 1.5 to 2 years by posting in the off-topic section. A large number of those users have now quit because they weren't able to participate in signature campaigns, while the merit system discourages spamming newbies who're simply after signature campaigns because they have no chances of ever ranking up.
I'm also here when there are a few signature campaigns and so much spam, people are very more interested in airdrops and bounty campaigns you'll see members with legendary accounts where all their posts are bounty reports, the merit system stops this ranking abuse, you have to be a good contributor if you want to be in a signature campaign, those who get in the signature campaign are privileged because they earned it.
They make the forum rich in content, other forum members contributed without a signature but it's their choice not to be part of a signature campaign.