Purpose of Steel?

Published on Monday, November 7, 2016 By fantstc1 In Offworld Trading Company

I'm a new player, and am working on the final practice mission.

I'm curious what the value/purpose of steel might be.

I don't see steel as something that is consumed when you upgrade (aluminum, coal, glass).

It doesn't seem to be a cost for patents and optimizations.

So, where does steel come into play?

Why would 50% steel advantage be significant... ever?