Because instead of ignorance and name-calling like your response, Bernie stands for social, economic, political, racial, sexual, environmental, and educational justice.
OK, if the Scandinavian countries aren't socialist, we can admit they have universal healthcare, universal education, daycare and nightcare, generous welfare, humanitarian jails and prisons, a really good equivalent to Social Security, close to gender equality, almost no homeless, equal funding for schools, and so on. I'll take that, whatever you want to call it. In the US, we would call that democratic socialism.