I don't know how relevant this is to Ethan Couch, but in Texas, a minor in possession or minor in consumption is essentially like a traffic ticket. You are not arrested and taken to jail, where someone has to come bail you out. There may be degrees, where if you are deemed to be intoxicated, you do find yourself in jail. But the jails are not big enough to hold all the under age drinkers that could be tagged for this offense. I'm not saying it's no big deal, but when you read that EC had a MIP on his record, it's not a serious offense relative to other offenses which can cause you a lifetime of grief. MANY of my D's friends in college got MIPs. They are a blip as long as they take care of it and don't get into any more trouble.
Thank goodness, neither of my Ds got MIPs or MICs in college. I really tried to stress to them that even though it's not the equivalent of a DUI or even more serious crime, both Ds want to go into careers which require a state license, and you do NOT want any hint of any kind of legal trouble in their history. Expunged crimes are still discoverable by certain licensing boards.