When I was on my first business trip at 18, I couldn't check into a hotel in Michigan by myself. I had to call me contact at (then) DaimlerChrysler to meet me for check in. I had a credit card that could buy a brand new car, but I couldn't get the key to a $75 hotel room due to age.

I later found out that, at the time, there was no law preventing me from acquiring the room, but the hotel policy was to not allow unaccompanied individuals under 21.