Restrictions on Second Amendment rights were politically viable for about 20 years as a response to rising urban violence (the big cities still, for the most part, maintain their anti-gun laws) and the racial politics of the '60s and early '70s. Consider California's 1967 Mulford Act, signed by Governor Reagan, which prohibited open carry and elicited an armed (but peaceful) protest in Sacramento from the Black Panthers.
Gun control was the offspring of liberal nannyism and racialized right-wing fears for law and order. The latter have had a different outlet in recent decades, with an emphasis on prisons and unleashing the unitary executive—when there's a Republican in office, at any rate—against subversives real or imagined at home and abroad. Safety-first liberalism by itself doesn't have the mass appeal to give gun control political currency. There are millions of gun owners, and unless millions more Americans fear they might be victims of gun violence, there won't be any national momentum for restrictions.
