Day by day, new members keep registering everyday. Only few of this member find it easy to rank up. Imagine an account opened for more than 2 year that still exist as a newbie.
I think that might be the cause of inactivity of such account or user and you still need at least 1 merit to get a junior member rank. Again, it might be because the account based only on the Alt coin bounty section of the forum and for such account they don't have any reason to rank their account up since there's no rank limits, before participating. Their only aim on Bitcoin talk is for bounty.
On the other hand, for someone who really wants to understand Bitcoin and plans on ranking up in the future, he or she has to be an active member and contribute where possible from their knowledge. As long as you follow all the rules of the forum, ranking up is possible.
The issue of Rank up in Forum is a little bit hard, now are days getting Merit in the forum is not all about performing task, but still if any wish to rank up it all depends on the person because everything in this life required hard work. What make them fear is the interval between the member and full member but still it not a problem. The OP write something about few of them do like to read and this can be considered the factors too.