Look at it another way round: If a Newbie or a Jr. Member created decent posts in places other than spam-megathreads, then he is likely to stand-out of the crowd very soon, since, to be frank, there just are not that many lower ranked members that make half-decent posts.

That is really an opportunity that one can grab, and all it requires is investing some time and, of course, having a bit of savoir-faire in him (logically, if the latter is absent, then there is not much hope). Obviously, one can’t expect to be merited on the first decent post he makes, but being consistent at it over a few days or weeks at most should do the job.

Now the common denominator of lower ranks (with decent exceptions for sure) is that they post like there is no tomorrow, with repetitive one-liners day after day. If they posted like the higher ranks that do get merited, then they would have no issue getting merits. There are also many high ranked members that do not get a single merit and wont. Have you noticed those?  Perception in the OP is likely biased too, having focused on observation of decent top ranked posters and likely ignoring the large amounts of them that go unmerited.