If we are to analyze it all there could be many reasons attributed to why this figures come to be, consider that the forum is such a platform that you can have a brief view on being a guest but the only restriction is that you can't post unless you're registered, out of the numbers that registered, many are spammer, scammers, trollers or any form or unserious category they could fit in, they would have registered to later discover the forum not to be as they have expected.
This is the main reasons some are leaving or getting banned, the forum is not like the social media they have freedom to misbehave, it not where they can plagiarize, neither are they permitted to make ponzi-like schemes on the forum, they never even thought about bitcointalk being regulated and moderated, so they will definitely leave for somewhere else, this is why the forum still maintain it's standard and reputation, the are to bed to the rules of the forum and not the forum to their own taste as they wish.
No, the newbies are coming onboard each day and are progressing doing well as long as you can adhere strictly to the rules, you can check out on the low ranking statistics from here from LoyceV The future of Bitcointalk: Low Ranking Top Merit earners in the past 30 days
That's not even a threat at all because most of the new members aren't yet familiar with DT or what it even means.
A little part of this may contribute to the statistics when they discovered that getting merits is not by default but needs to be earned, they may not have that skill, time or knowledge and sacrifice to give in other for them to earn merit over time.
this is the highest portion of the forum threat to many people who cannot be law abiding or behalf in an unregulated manners and wouldn't want to be corrected, warned or restricted in doing some particular things.
bitcoin adoption is increasing everyday and the more are people putting interest on learning about bitcoin everywhere, but when they get to the forum like this, it appears to them that they meet the whole thing entirely different from the perspective of how how they're viewing ot before coming.