Simple, like every social media site, they're are barriers on this site that prevent exposure to new users and content they generate. Depending on what kind of content you want to post here. Reddit has its karma system to force feed content you're supposed to see, YouTube has its algorithm that insists on regular uploads, which of course alienates animators, so all you're allowed to watch is sssniper wolf react to crap and hear moist critical's bland over valued opinions on stuff no one cares about.
Newgrounds gots it's scouting system, and combine that with the website's filters and no new user gots a chance in hell of getting any exposure here, unless the people running this site want you to be heard or seen. The common denominator is, you consume content the website owner wants you to consume, and they got barriers to make that happen. Newgrounds getting more traffic now, because a handful of select animators are getting exposure they can't get on YouTube.