Steel does work (when done right) but Brass is best
And that's it right there. Brass cases work better. Steel works acceptably well, if done right. The problem is that since its the cheapest stuff, its not always done right. Steel cased ammo isn't just the cheapest ammo because steel is cheaper than brass. I believe they save costs in other ways as well.
I'm a reloader, and I don't even use Berdan primed brass, if I can help it. I don't shoot steel cased ammo. I don't shoot aluminium cased ammo. And most of the time, I don't shoot lower cost factory brass ammo. I also don't shoot anyone's reloads, except mine. And that includes professional reloading companies.
I'm cheap about somethings (clothes, cars, food, etc...) but not about what I put in my guns. There is low(er) cost, and then there is cheap. MY reloads are lower cost than factory ammo, but they aren't cheap ammo. Cheap ammo is false economy, to me.
Brass cases have the best combination of all the factors needed, better than steel, better than copper, or iron, or any of the other materials that were used when cartridge cases were being developed. Steel cases came about basically as a wartime production stopgap, something that would work acceptably well (particularly in high volume arms like machineguns) and was a way to save brass for more important things than small arms ammo.
Since it does work well enough, usually, several nations (notably communist ones) adopted steel as the standard for small arms. No longer communist, those countries are now selling steel ammo to the rest of the world. Cheap.
There was virtually NO (cheap) steel cased ammo in the US before the fall of communism. Today its everywhere, and competition being what it is, price matters to many people, for some things, its the overridding factor.
Note the dominance of steel cased ammo in ALL calibers!??? Go ahead, take a look....
I don't see much steel cased ammo in non-military calibers (ours or theirs). Where is the steel cased .44 Mag? Where is the steel cased .32acp? .357 Mag? (and where is the steel cased ammo in commercial sporting rifle calibers?)
Steel cases are NOT superior to brass in anything, except cost. You can run a Porsche, or even a Volkswagon on 70 octane fuel, and it will still get you from point A to B, and (hopefully) back again. But it will run better on the more expensive fuel it was designed for....