Mexico is a country well known for criminal activities like drug trafficking and other organized crimes. In the recent time, Mexico has witnessed a positive growth in their economy, but the problem still lies at the increasing rate of criminal activities in the country. The reason why Mexico is still crime ridden despite good economy is because of the activities of the cartels have not totally controlled.
You don't expect those who involved and benefited in drug trafficking and other organized crimes when the country economy was very bad to stop their operations because the economy is now looking good. Also people seem to be benefiting from all these criminal activities, what you stand to gain when you engage yourself in it is quite more than what you would realize when doing all other legitimate businesses. Most crimes in Mexico are directly or indirectly as a result of the activities of cartels.