A fuge was originally designed for the purpose of providing pods a safe place to breed, lacking of predation, hence the term refugium from the word refuge.
The other benefits are secondary, yes macro will help w/ nutrient export, but it takes a fair amount for significant results in that area.
My thoughts are hey, we all go as big as we can for a sump for water volume/stability/gear, and if you have space it's really nothing more than adding a baffle or two, so why not have one, I mean the benefits are great, PH stability, and one of the best constant live food sources in pods.
Even if you don't keep mandarins other fish will eat them, I see my anthias peck at them, my copperband too, I'm sure others do too, and if you do keep mandarins or the ruby red dragonettes or similar a fuge is essential.