Why use a heating block? Is a heating block necessary for heating small chemistry samples? I figure it helps a ton (not to mention it stabilizes too) in getting heat to the reaction but is there anything else it does?
You have already mostly answered the question yourself ;)

A heating block, made from a material with a high thermal conductivity, helps to keep (a lot of) samples distributed over a larger area (several vials, Eppendorf tubes, etc.) at exactly the same temperature even if the primary heat source is punctual or just a layer of heating wires at the bottom of the instrument.