Because they become teenagers. And then they whine and cry at the ice cream stand because vanilla is just "GROSS!" and won't eat anything with vanilla in it. To the point of tears. And instead of just taking the ice cream and being grateful, they throw a temper tantrum, to the point of tears. And they have no consequence to the action of not knowing what was in the flavor of ice cream they chose.
So we went to get ice cream after a very wonderful bike ride. Ahead of us stood super soccermom waiting in line (complete with the Abercrombie and Fitch capri's and the nike running tank) with her pre-teen devil-spawn with arms crossed in the stance of "I don't want ice cream". Super soccermom can't decide what type of ice cream she wants so devil spawn chooses something, and doesn't know what is in it.
The ice cream comes to the window, and SSM gives it to this girl who bursts into tears and REFUSES to try the ice cream because it's WHITE which automatically means it's VANILLA and VANILLA is just GROSS. So SSM says "It's ok, what do you want then?" and passes the ice cream off to Super SoccerUncle, who eats the ice cream on top of the ice cream he just finished. Now, don't get me wrong...I have been served the wrong flavor, but instead of throwing an all out hissy, tried it, and a couple of times, it was the best error ever made. However, "back in my day", My ass would have been blistered, and I would NOT have gotten any other ice cream. Not because I couldn't make a decision, but because I threw a hissy fit. The lesson learned would have been "Find out what's in the ice cream before you order, and be grateful to your parents for even taking you out for ice cream".