Socialism is still very demonized in American politics. Try to get into a position of power while describing yourself as a socialist (and I mean an actual socialist eg. ending the Cuban embargo, supporting left-wing movements across the world and advocating for the end of capitalism).
Also neither Bernie nor any democratic politician is a actually socialist, they are still very capitalist. At best they are for "capitalism with a human face)
Cool.
Biden is not in favour of any of that.