The facts of those complex problems are uncomfortable and nobody really wants to come to grips with them.
For example, we don't really have a single America with a moderately high rate of gun deaths.
Instead, we have two Americas, one of which has very high rates of gun ownership but very low murder rates, very comparable to the rest of the First World democracies such as those in western & northern Europe, Australia, New Zealand, Canada, Japan, South Korea. The other America has much lower rates of gun ownership but much, much higher murder rates, akin to violent third world countries.
The tough questions are those like, why do we have these two Americas?
But that's an uncomfortable discussion to have. So instead those on the left favor simple minded restrictions that target first world America, with its high gun ownership but very low murder rate, but don't address the root causes of third world America's violence at all.