Why can't normal people own guns in NYC?

i live in NYC and it sucks that only the thugs and the NYPD thugs get to carry weapons... If everyone over 18-21 had weapons (except sick people or felons) the world would be a safer place! right now that guns are restricted we still get shot so wtf? this just means that normal people can't get guns to defend themselves (even if they try to legally) but people that want to harm others can easily! what about the 2nd amendment?...