is that for me?

I've been curious how many sales are the result of an unspoken law of the household. Namely that it is unacceptable to upgrade your stuff without upgrading their stuff. The debate likely ends with: "Yes you can use my old one." but a non-trivial fraction must result in a second trip to the store. I noticed while at the Apple Store myself picking up my computer from repairs that a family had purchased 4. One for each of their 3 children and presumably one for the wife. The poor associate had to sit through the "I want the blue case! No I want the blue case!" onslaught. Do 5-6 year olds each need one because the parents aren't willing to teach them to share? When they get older will that expectation learned in early childhood carry forward?