Because it’s not as a big a problem as you’d think. El Salvador had gangs victimizing entire communities. Why? Because the gangs didn’t have a source of income aside from low level extortion. In short, the El Salvadoran gangs were financially unsuccessful, desperate bands of young men. Eventually, after incarcerating tens of thousands of young men without real due process, in conditions that are inhumane, they’ll have to release the vast majority. The same thing happened in the United States after the paranoid prison boom of the 1990s.
In Colombia, the communal violence of the 1980s and 90s is long gone. Tourists are literally safe walking around communities that were no-go zones 25 or 35 years ago. I’ve even read that small scale personal use possession and sale has been defacto decriminalized in some parts of Colombia. In short, it’s not a big deal anymore. It’s also not as economically significant. The drug trade is increasingly economically insignificant compared to petroleum.
What solved the violence issues in Colombia? Political settlements worked, even with reverses in recent years. Economic growth did wonders as well.