There's a myth that higher rank users don't need merits and that myth is mostly spread among the lower rank users, Personally I hardly receive merit from lower rank users although they are those i try to merit the most. The average lower rank users prefer hoarding their smerits instead of sending it out and some possible reasons for this act are;

• Since they don't get merits on regular basis they won't see the need in sending the same merit they don't get to others.
• Like you have previously guess, they see merit sending as a job for merit sources
• They think the system isn't fair to them therefore they decide not to partake in meriting others

But they fail to realize just like in the real world, givers never lack. If you want something learn how to give that which you have out. That's my advice to them (those that have at least 1smerit to send).

I remember getting advice on this issue few months back when I was still a member rank user.