Are you a real adult if you're still on your parents' family phone plan?

Millenials who stay on their parents' phone plans should feel good.

Kathrin Ziegler/Getty Images

• Millennials, some now into their 40s, are still on decades-old family phone plans.
• Sure, this can seem like arrested development or mooching. But really? It's just smart.
• There's no reason not to save a few bucks on a phone plan.

Before you yell at me, let me first say that I am not, and have never been, on my parents' cellphone plan. (I didn't get a cellphone...