They use the word because it sounds good. All steel contains carbon, that's what makes it steel. A higher carbon content can make it stronger but also more brittle. It's all in the heat treatment.

This is not an argument, it's fact. Steel is and always will be an alloy of iron, carbon and in some cases other metals like chrome and molybden (ChroMoly Steel) or vanadium.

Just search for the definition of steel if you don't believe me.