Mahjong Rank & Rating Questions

I just started playing Mahjong in FFXIV and am currently 6th Kyu with 1546 rating points. What I am trying to figure out is, why is rank important? All of the achievements require rating, not rank. Do advanced ranked matches have a higher rate of rating rewards than novice ones? If outranking your opponents means you stand to gain less rating from a win & lose more rating from a loss, then isn't rank basically a detriment?:confused:

Ranking only affects eligibility to play Advanced matches, I think.

The rating seems to be based on the ELO system but I'm not sure how it works in practice since you can win if you end 1st or 2nd but lose in 3rd or 4th.