I am continually amazed at how many easy-to-ID observations sit at Needs ID for weeks, months, years, and yet my notifications are filled with identifiers adding the fourth, fifth, sixth ID to observations already at RG - and I’m talking mostly about plants here!
Now, my bias is to ignore RG observations and work only on Needs ID, but I can understand why people add a third agreeing ID to an observation; that helps ensure a RG observation stays as RG even if one of the identifiers deletes all their own IDs. More agreeing IDs than that seems like a waste of a good naturalist’s time (feel free to present evidence to convince me otherwise!).
I will say that it’s likely that two things contribute to what you’re seeing: First, at least for the northern hemisphere right now, it’s summer and everyone’s out making observations of their own, rather than making IDs.
Second, I get the impression that many identifiers, including me, start at the newly added observations for their area and work backward in time. When I do that for everything in New England, I run out of time or enthusiasm around page 20. Sure, IDers might filter for Birds or Lepidoptera or Plants, but they rarely filter for single species or genera. I just went and filtered for Needs ID American Robin observations in New England now, and there are 20 pages of them, with 30 observations per page. Now, I bet lots of the older observations are of eggs or empty nests or young nestlings or maybe feathers - observations that are hard to ID, in other words - but I bet many of the first few pages’ worth are easily identifiable.
And, of course, we always need more identifiers. Even in summer, there are days when it’s too hot to go hiking or the contractors are here to work on the house - perfect times to make lots of IDs!
ETA: Well, I went back to the Needs ID American Robin observations and in fact, even the most recently added observations are mostly eggs or nests! So I picked a bad example - the birders are clearly on top of their identifying game!