I don't share the opinions here that the reason is control-related. I think they simply want to reduce gun-related deaths. No guns=no gun deaths=less deaths overall (fewer successful suicides, less accidental deaths, perhaps reduced lethality of criminal violence that will still occur, less fear of being an accidental victim, and less social cost of the above).
only the naïve think that way. the ones in power think about maintaining that power by control.