The question should probably be "Why not be Mango?" as the reasons why number in the teens. But since you asked...
Everyone is dong it. Yes, everyone is doing it so peer pressure and the threat of social ostracism will be important factors in your decision to be Mango.
Secondly, there is no evidence to suggest being Mango causes additional risk to pregnant women. Through a series of self administered double blind tests, the Mangoes found the evidence inconclusive and have therefore concluded there are no additional risks to pregnant women.
Finally, the Mangoes are about to be legalized in Colorado.
So there you have it. Being Mango is not really a lifestyle so much as a decision one makes when confronted with "group think", inconclusive evidence and local or state legislation.