That's primarily because gun bans or gun control are a net benefit whilst letting your poor and old starve is a net negative.
If you really believe that, compare/contrast most dictatorships with the United States, Switzerland, and Israel.
Gun control is something that oppressive rulers always try to implement as soon as possible.
However, all (as far as I know) totalitarian states have strong gun control laws. I can't think of a single one which had a permissive attitude toward the civilian ownership of guns.
I'm speaking of course of de jure gun control laws, not the de facto possession of guns by the population.