The reason for that is that the highest level affixes are useless (like 30 Frostarrow charges for example) and therefore you have to pay attention to the item level of the gloves. I know for Hit Power Gloves that you don't want the Affixlevel of the Gloves too high and I suppose the same thing applies to Blood Gloves.
I want to craft Hit Power Gloves and Blood Gloves.
