Heroin is less social than alcohol. You don't go on a date and take heroin. Because the effects don't match what you want. To be fair you don't go on a date and take cocaine really either, because you "won't work". Parties with only cocaine or heroin would suck.

But yes they are more dangerous to the individual and would be more dangerous to society if everyone decided to start overdosing heroin all the time! But they'd all die and then alcohol would be back at number one.