Any glove used on the hand swinging the hammer requires the hammer to be held more tightly causing muscle fatigue, possible tendonitis, and potentially carpel tunnel syndrome.
If a glove is used around hot steel and the glove gets wet, the steam will burn before before the glove can be removed. This is especially true of the plain leather gloves.
I like the Kevlar glove for my right hand, as I am left handed, not for the sake of the heat, but rather to prevent the tiny cuts in the palm from holding the end of poorly deburred barstock.
As I work in the medical field, I also need clean hands. Coal, charcoal, the really dirty black dust from sanding scale, and used Harley oil, all come off with a wire brush. Please note, the wire brush comment is meant in jest and is not advised. I actually use a GoJo- like waterless hand cleaner so my spouse will let me back in the house. I then use bar soap and a stiff nylon brush. No problem.