Why Most Elemental Damage And Status Effect Systems Are Pointless

This primarily applies to RPGs (Western ones, I've never really played a JRPG, it's possible they implement it way better, I wouldn't know).

The idea itself isn't bad in theory, but somehow whenever I see a game use it, the system serves no practical purpose.

It's The Economy, Stupid: Variety In The Binding Of Isaac And Other Roguelites

I enjoy most genres, but roguelites/roguelike-likes are a particular favorite of mine. I'm drawn in by multiple qualities: the real choices and consequences of permadeath, the focus on solid gameplay instead of narrative or visuals, the tendency for multiple short playthroughs keeping the experience tight. And the way these games make use of procedural content to offer a huge variety of scenarios, letting me fully explore a set of mechanics. And in the variety department, no other game in the genre has been able to top the sheer replayability of the Binding of Isaac (the first game or Rebirth). I often wonder why that is. When other roguelite games have tried to use Isaac's formula, or some choice bits of it, none of them really came close to the same potential for different playthroughs. They appear to just copy some shallow elements of BoI's gameplay, seemingly without understanding their purpose in the overall system.

So what is this system, exactly? What makes each playthrough in Isaac so different from the last?