Though `H_(2)` is a good reducing agent why is it not used as a reductant in metallurgy?

Explanation

When `H_(2)` is used in the reduction of a metallic oxide, itself gets oxidised to `H_(2)O`. Change from gaseous to liquid state decreases `DeltaS`:
`MO(s)+H_(2)(g)rarrM(s)+H_(2)O(l)`
`therefore" "Deltas=-ve and DeltaG` becomes less `-ve` (increases).
So, thermodynamic feasibility of the reaction decreases.
Absorption of `H_(2)` to form a metal hydride also decreases its tendency to reduce metal oxides and so not used in metallurgy.