Your statement is true to some point. You'd be surprised what some car makers refer to as "young", for some it's late 20's to early 30's. At that stage a lot of people are in the stages of getting married and having kids. Making a vehicle like the Q30 good for a number of years till something like a QX30 is needed.I think that the Q30 is meant for "youth" as in young couples or singles who don't yet have a family. Youth that are a bit more concerned with style than cargo space or practicality.
The QX30 and QX50 are more for families. Easier access to the back seat to get kids in and out. More of a soccer mom feel.
Just my 2 cents.